Lots of beings have some kind of weakness such as a weak spot, a specific Kryptonite, a Weaksauce Weakness, etc. However, not every weakness is obvious or well-known, and beings that seem like they should have a weakness might turn out to not have one at all or not have one that's expected. This will usually come to a surprise for anyone who tried to take advantage of what they thought was a weakness.
There are multiple reasons why someone might mistakenly think a person or group has a weakness they don't. If members of a group of beings generally have a weakness, they might be shocked when specific individuals or subgroups don't share it. Alternatively, if an individual or a subgroup of beings has a weakness, then someone might mistakenly believe everyone in the wider group has the weakness. Other times a person might assume that someone suffers from a weakness due to a misunderstanding or out of context information.
There are multiple specific contexts this trope can appear. A Hunter of Monsters whose knowledge comes from folklore or pop culture might believe that a monster has a weakness that it doesn't have. Someone who wants to kill someone with their allergy might try to kill someone with what they think is their allergy. Someone facing a superpowered person might assume that their power has a Logical Weakness that they don't have.
Super-Trope to Fake Weakness, which is when someone deliberately pretends to have a weakness they don't have. See also Removed Achilles' Heel, which is when someone who once had a weakness no longer has it. Compare Mistaken for Overspecialized and Power Misidentification. See also No-Sell. If someone thinks a person has a weakness through being Genre Savvy, only for it not to work, that's Wrong Genre Savvy. Has nothing to do with one being perceived as weak and helpless, that's Underestimating Badassery.
Examples:
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Anime & Manga
- Black Cat (2000): After Creed mortally wounds Nizer's partner Ash with the first mode of his Imagine Blade, an invisible katana, Nizer gambles that since Ash's blood is on the blade, he can still see the size and shape of the sword from said blood. Unfortunately for Nizer, the Imagine Blade is an Empathic Weapon that can reshape itself, allowing Creed to impale Nizer from a distance by making the blade longer.
- Hellsing: During Alexander Anderson's first fight against Alucard, Anderson uses his holy bayonets, which stops a vampire's regeneration, to cut off Alucard's head. Having killed several other vampires this way, he assumes that's that, but Integra tells him that Hellsing's experiments have enhanced Alucard to be far more powerful than the standard vampires Anderson's fought, and sure enough Alucard manages to restore himself whole after a few minutes.
- JoJo's Bizarre Adventure: Stone Ocean: During Jolyne's fight with Viviano Westwood, the latter uses his Stand Planet Waves to summon meteors to attack. Jolyne believes that his Logical Weakness is that the meteors will hurt him if he's in their path, but Planet Waves has another power that causes the meteors to disintegrate if they get close to him.
- Kill la Kill: Gamagoori's Three-Star Uniform powers him up the more he's hit. Ryuko figures his Logical Weakness would be that if she simply stops attacking him, he won't be able to power up anymore. Gamagoori promptly starts attacking himself, which has the same effect as if Ryuko attacked him.
- My Balls: At one point while faced with what he thinks is a vampire, Kohta uses an Improvised Cross with his erect penis and a scalpel to try and ward it away, assuming it's a vampire. It doesn't work because the creature is a succubus and not a vampire.
- Overlord (2012): A recurring issue caused by Nazarick inhabitants having endboss stats in a low-level world.
- A group of (relatively) high-level evil adventurers confronting (well, getting their asses handed to them by) Sebas think his prowess in unarmed combat comes from magic gloves. Their thief successfully steals his gloves, only to find out that Sebas' gloves have nothing to do with it, he's just that fast and strong.
- Jircniv believes Ainz to be a Squishy Wizard of immense magical power but corresponding physical frailness. He arranges for Ainz to fight the arena champion (a trained war troll) without magic... and has a minor breakdown on seeing Ainz easily solo the troll (unbeknownst to him, Ainz also has a spell that actually turns him into an even better but Magically Inept Fighter). This leads him to realize there really is no hope of getting rid of Ainz, so he becomes a Voluntary Vassal. This turns out to be his best idea ever.
- Shaman King: Team X-III go through great lengths to discover what Hao's medium is, as they assume that it's an object that can be destroyed so that he can't summon the Spirit of Fire. However, Hao reveals that his medium isn't actually a solid object; he uses the oxygen in the air itself to summon the Spirit of Fire.
- Yu-Gi-Oh!: During Yami Bakura and Yami Marik's duel, Bakura manages to send Yami Marik's ace card, the Winged Dragon of Ra, to the graveyard, which he assumes makes it useless because he knows that one of Ra's abilities is that it gains the attack points of the monsters used to Tribute Summon it, and he assumes that it's powerless if summoned from the graveyard. However, Yami Marik reveals that Ra has hidden abilities not written on the card, with one of them being the ability to convert his life points into Ra's attack points, and he uses this effect alongside others to win the duel.
Comic Books
- DC × Sonic the Hedgehog: While Sonic and his friends are stuck on the DC Universe, Lex Luthor calls over Knuckles to discuss something. Since Knuckles is wearing Superman’s costume, Luthor believes he’s a Kryptonian and, when the echidna arrives, surprises him with a green stone. Turns out the stone is the Green Chaos Emerald and not Kryptonite and it takes Knuckles a bit to realize he was trying to poison him.
- Power Girl: One comic has the titular heroine trying to take out a group of robots designed to destroy anything imperfect by stating that since they are imperfect, they should destroy themselves, like in Star Trek. It doesn't work because they were designed to be immune to "stratagems from old ''Star Trek episodes", forcing her to take them out the hard way.
- Spider-Man: When Carnage first appeared, Spider-Man thought he had the same weaknesses as Venom (i.e. sonic attacks and fire) due to the Carnage symbiote being spawned by the Venom symbiote. He was unpleasantly surprised to discover that compared to Venom, Carnage is resistant to sonic attacks and leaving fire his only constant weakness (Carnage is shown to be vulnerable to sonic attacks, but not nearly as much as Venom is).
- Superman: While Superman and other Kryptonians are weak to Kryptonite, it's stated that they are only weak towards Kryptonite from their own universes.
- Inverted in Legion of 3 Worlds, when Threeboot Element Lad turns rocks into Kryptonite to try and stop Superboy-Prime, Prime laughs it off before he realizes to his horror that its affecting him, which doesn't make sense. At the end of the story, it's revealed that the Threeboot Legion hails from Earth-Prime, which is why it affected Prime.
- In the 2021 Suicide Squad run, Bloodshot attempts to stop Ultraman with a chunk of Kryptonite. However, alternate Kryptonite empowers Ultraman, which he does by crushing it and snorting its remains like a line of cocaine.
Ultraman: ...my favorite.
- Uncanny X-Men (1963): One story pitted the team against Dracula. In an attempt to ward him back, Wolverine, Kitty Pryde and Nightcrawler all attempt to use crosses. Wolverine’s doesn’t work because he doesn’t believe in it, Kitty’s doesn’t work because she’s of the Jewish faith, but Nightcrawler's does because he’s a devout Christian.
Fan Works
- Dungeon Keeper Ami: When Ami hears about vampires' weakness to sunlight, she thinks about using UV lights as a substitute, but the weakness isn't for any scientific reason, but due to how the power of the God of Good collective is part of sunlight in the world she's in, so "artificial" sunlight doesn't work.
- Total Drama Comeback Series: In Battlegrounds, during the vampire-hunting VR challenge, Arthur, Carol, and Clive are attacked by Dracula. Clive tries to use the flashlight on him, but all it does is make him sparkle. Arthur's last words are "We had our butts handed to us...by a Twilight vampire!"
Film — Animated
- Bolt: Bolt the dog unknowingly stars in a TV show (which he believes is his real life) and the show’s crew has used props and special effects to trick him into believing he has superpowers. When Bolt escapes the TV studio and finds that he can’t use his "powers" anymore after being covered in styrofoam packing peanuts, it makes him think styrofoam drains his powers.
- How to Train Your Dragon (2010): Because all of the other dragons have blind spots, Fishlegs assumes that the big "queen" dragon he and his friends are fighting will have one too, but it doesn't.
- The Incredibles 1: Being The Sociopath that he is, Syndrome regards mercy as a weakness and calls Mr. Incredible's bluff when the latter threatens to kill Mirage unless Syndrome lets him go. Later, a disgusted Mirage tells Syndrome that mercy isn't a weakness and disregarding life isn't strength, leading to her pulling a Heel–Face Turn.
- Megamind: The titular character briefly traps Hal in a copper sphere after Hal has been accidentally given superpowers derived from Metro City's former resident superhero, Metro Man, and is shocked when the copper has no effect on Hal (who tears his way through the sphere like it was tissue paper). Justified, as earlier in the film, Metro Man led Megamind to believe that all the copper he was surrounded by was his only weakness as part of a scheme to fake his own death.
- Night of the Zoopocalypse: When Dan gets turned into a Gum-Beast and attacks Gracie, he gets drenched in a sink full of soapy water while a radio is playing the Cole-Pepper Zoo Closing Song. This accident turns Dan back to normal, Gracie realizes that soap and water can cure the Gum-Beasts. She and her friends gather all the Gum-Beasts and drench them with soapy water, but this fuses them together into a giant Gum-Beast.
Film — Live-Action
- Star Wars: Early during the Clone Wars, Republic forces believed the B1 Battle Droids fielded by the Confederacy of Independent Systems to be the lesser threat compared to the B2 Super Battle Droids. This is because of the Battle of Naboo, where the destruction of the main computer that issued orders to the B1s led to the entire battle droid army shutting down. This led to desperate surgical strikes aimed at destroying the CIS main battleships or flagships, thinking that would lead to a (comparatively) easy victory. Unfortunately, it became clear that the CIS also realised that particular weakness was a problem, and had upgraded the B1s to no longer be reliant on a signal from a main computer. A side effect of this gave the B1s more personality compared to the older models.
Literature
- Aesthetica of a Rogue Hero: Some enemies like Phil attempt to use Anti-Magic defenses to stop Akatsuki, unaware that he doesn't use magic, he uses Ki Manipulation, and anti-magic doesn't stop ki attacks.
- Discworld:
- In Witches Abroad, Lilith is convinced that Granny Weatherwax, Nanny Ogg and Magrat Garlick will inevitably lose in the end — simply because they are evil, and in fairytales, evil is always defeated. It never enters her head that a) she lives in a Fractured Fairytale world b) more importantly, she is the truly evil one.
- In Going Postal, Moist is told that on his parole, he'll be constantly watched by Mr. Pump, a golem, and any attempts to go back to his conman life would be harshly stopped. Moist is at first shocked at that, since he believed golems can't hurt people. Lord Vetinari corrects him: golems can't do it unless authorized.
- Goosebumps: In "Revenge of the Lawn Gnomes", Joe's dog Buster is licking one of his dad's new lawn gnomes, so he uses a dog whistle to get him to stop. As Joe picks up the lawn gnome, it gives a terrified expression and reverts back to it's smiling self. In the climax, Joe and company are surrounded by an army of gnomes. He uses his dog whistle to get Buster to attack the gnomes, thinking that they're afraid of dogs. It turns out that the dog whistle just freezes the gnomes forever and it's their real weakness.
- Mistborn: The Original Trilogy: Kelsier's plan to defeat the immortal, overwhelmingly powerful Lord Ruler hinges on legends of an Eleventh Metal with unknown powers in allomantic magic. It turns out only to grant visions of other people's past; the rumours of it being a mysterious Immortal Breaker were a Red Herring spread by Ruin to incite rebellion.
Live-Action TV
- Cobra Kai: In the Season 4 finale, Terry tells Kreese that Johnny Lawrence is his weakness and what's holding him back. Kreese later retorts during his final confrontation with Terry in the penultimate episode that Johnny is a source of strength, proven true when Kreese sacrifices himself to kill Terry so that the latter doesn't hurt Johnny and his family.
- Doctor Who: In the episode "Dalek", several human characters flee the titular creature up a flight of stairs. Due to its lack of legs (Daleks have often been nicknamed "dustbins" or "tinpots" by fans due to their shape), they assume they are safe. One of the humans tries to negotiate while another mocks it for being foiled by something so simple... at least until the Dalek demonstrates it can fly. The trope also extends to the audience, as stairs really were the Daleks' weakness in the original run of the show; as such, the Dalek declaring "EL-EV-ATE!" is a Wham Line.
- Goosebumps (1995): In "Welcome to Dead House", Amanda thinks that the wreath in her new house is the cause of the zombies. She burns the wreath in the fireplace, hoping this would destroy the zombies, but that doesn't stop them.
- Star Trek: Deep Space Nine:
- In the episode "Valiant", Red Team believes that they have found a weak spot in an experimental Jem'Hadar warship and ready an attack run with their Defiant-Class, including modifying their torpedoes for what they think is maximum efficiency for the strike. Unfortunately, either the weak spot never was one to begin with or the Jem'Hadar figured out its existence and reinforced the armor because the attack run does not work. The warship opens fire after disappearing in a huge explosion for a few seconds, curb-stomping the Valiant and killing almost all of Red Team, and depriving Starfleet of valuable intelligence on the new warship.
- Then in "Tears of the Prophets" the Federation Alliance sees a potential weak spot in the Dominion defenses around Chin'toka system and figures that's the best place to take the war to the Dominion. What they didn't count on was all the automated weapons platforms seeded in orbit around the system's planets, which savage the Alliance fleets before the Defiant finds the fatal flaw in the weapons platforms and wipes out the system's defense grids.
Toys
- Transformers: Starscream is famous for his cowardly streak, and this is viewed as a core aspect of the character throughout most of his iterations in the franchise (one of the few Starscreams with no cowardly aspects is the one from Transformers: Armada). However, some media take pains to remind people that Starscream is second-in-command of the Decepticons for a reason. For example, the IDW Publishing comics had a Decepticon mock Starscream for being a coward and an opportunist, only for Starscream to observe that his fatal mistake was giving an opportunist an opportunity as he split the Decepticon's head in half. This actually hearkens back to the original toy bio for Starscream that notes that Starscream's actual weakness is that he gets overconfident in his abilities, but he's still extremely dangerous.
Video Games
- The Elder Scrolls IV: Oblivion: It is real-world myth that vampires are harmed by garlic, and therefore warded off by it. So it may come as a surprise to anyone playing the Elder Scrolls games that vampires in Tamriel are not weak to garlic. We know this because of Vicente Valtiere, a vampire and member of the Dark Brotherhood. In a letter he wrote to a fellow Dark Brotherhood member that you can find in his quarters, he laments that he is the only vampire (who he knows, at least) who is harmed and weakened by garlic. Therefore, we learn this fact about Tamriel vampires from one who inverts this trope; Vicente, rather than not having a weakness you would expect him to have, does have a weakness you would expect him not to have since no other vampire has it.
- Fate/Grand Order: Due to the nature of their legends, the Scandinavian hero Sigurd is destined to be killed by his wife's Noble Phantasm, Brynhild Romantia, should it be used against him. While it deals severe damage to Sigurd, it doesn't kill him when Brynhild uses it on him in the second Lostbelt. This is a signal to everyone that something is very wrong with Sigurd. Indeed, while it did in fact shatter Sigurd's Spiritual Core, Sigurd's body was being used to contain the omnicidal Surtr. Brynhildr's attack was the last thing needed to free Surtr to continue his rampage.
- Vampire: The Masquerade - Bloodlines: At one point The Mandarin, the leader of the Fu Syndicate, kidnaps the Player Character to study how to kill vampires. Some of his methods of doing so, while based on actual knowledge, are partly flawed due to a misunderstanding of how said weaknesses work. One test has him trying to use U.V. lights, which he assumes will work because it's physically the same as sunlight, which doesn't work because the vampire's weakness to sunlight is mystical and requires the actual Sun. At another point he has an underling hold a cross to ward them away, which doesn't work because vampires are weak to True Faith and not crosses specifically.
Visual Novel
- Fate/stay night: Discussed; Tohsaka Rin explains to Shirou that the reason why Servants are known by their class and not by their names is because knowing a Servant's true name also clues an opponent as to their strengths and weaknesses. However, she also notes there are some Servants who can perform beyond what is expected of their class, and so it's dangerous to make assumptions based on whatever their class is. Archer is an example: While the fact that his class is Archer would suggest that he's a long-range specialist, he's actually quite competent at close quarters combat. Similarly, Lancer is armed with a spear, but due to his true identity he is actually extremely dangerous at long range as well.
- Henchman Story: Invoked by Shining Nova. As part of her Awesome by Analysis shtick, Lady Scorpion checked every bit of information on Shining Nova's previous battles, and identifies Nova's Calling Your Attacks tendencies as the biggest weak point. Notably, she doesn't think that it's a particular weak point Nova has, simply that it's the area where she believes she has the biggest advantage (i.e. if Nova has to vocally command a weapon or attack to activate, Lady Scorpion has a few precious seconds to dodge or counter the attack). It's implied later that Nova only uses voice commands for particularly powerful attacks in order to avoid accidentally triggering them, and that the voice commands can be disabled when necessary (e.g. against a especially dangerous opponent like Lady Scorpion where even a split-second delay can be costly).
Web Animation
- DEATH BATTLE!: In "Tigerzord VS Gundam Epyon", at one point Tommy tries to attack the gem in the Epyon's chest because he assumes it's a weak spot. It doesn't work, as it's just a decoration.
Webcomics
- Grrl Power: Vehemence hits Maxima with a massive lightning attack
and notices that her strength has decreased. He concludes that electricity weakens her. The truth is that the sheer magnitude of the attack forced her to shift all her power into defense.
- The Order of the Stick: Played for Laughs when Crystal tries to kill Haley with a pickle, her reason for believing Haley would die from it being that Haley never ordered pickles on her sandwiches, which must mean that pickles are her one weakness. (In all fairness to Crystal, though, some people are physically vulnerable to pickles — though Haley doesn't have an allergy, she simply doesn't like them.)
Web Videos
- Dragon Ball Z Abridged: When fighting Vegeta in his giant ape form, Goku thinks the increased size means he'll be slower. He is very much wrong.
Western Animation
- BattleTech: When the Jade Falcons attack Sommerset, Adam Steiner and his team note how their BattleMechs have superior armor and firepower and guess that this must have come at the expense of their heat dissipation systems, so they try to trick the Falcons into overheating in the desert sun. Unfortunately for them, Clan heat sinks are superior to Inner Sphere heat sinks so the Jade Falcon mechs were able to keep firing without issue, while Adam Steiner's forces quickly became overheated themselves.
- DuckTales (1987): In "Robot Robbers", a group of robots built by Gyro are stolen by the Beagle Boys and Ma Beagle who use them to go on a crime spree. At one point, Scrooge and Glomgold try to use water to short them out like with the previous robot built by Gyro. Unfortunately it doesn't work, and Gyro only remembered now that he made these robots waterproof.
- Freakazoid!: In ''Hero Boy", Gutierrez tries to use green kryptonite to weaken Freakazoid, until Freakazoid points out that would be Superman’s weakness. He then pulls out a page of yellow sticky notes, thinking it’ll subdue him, but with Freakazoid then saying the color yellow is the weakness of Green Lantern. Gutierrez splashes a glass of water in Freakazoid’s face, with Freakazoid obviously saying that is the weakness of the Wicked Witch of the West. Freakazoid gets so frustrated by these mistakes that he outright tells Gutierrez how to weaken him… and even help build the cage to do it.
- Futurama:
- In "A Tale of Two Santas", Leela assumes that since Robot Santa is a robot, it means she can trick him into destroying himself with a logical paradox. It doesn't work because robot Santa was built with paradox-absorbing crumple zones.
- In "Where No Fan Has Gone Before", the Planet Express and Star Trek crews are being attacked by Melllvar, an Energy Being obsessed with the show. They figure that feeding him more energy will cause him to overload, "like putting too much air in a balloon", but instead it just powers him up.
Fry: Like a balloon and... something bad happens!
- Jackie Chan Adventures: In "Chi of the Vampire", the heroes are visiting a Haunted Castle and encounter a Jiangshi . At one point Tohru breaks off a piece of a banister to use as a Wooden Stake, but Uncle says it won't work—a Jiangshi is a Chinese vampire and has an entirely different set of weaknesses.
- Mega Man (Ruby-Spears): In the first episode, Dr. Wily believes that all robots are programmed to be unable to lie. Megaman, who has been captured, is able to use this assumption to trick Dr. Wily into freeing him.
- Superman: The Animated Series: In "Bizarro's World", at one point Superman while in his lead suit tries to use Kryptonite to subdue Bizarro, who is a mutated clone of him. It doesn't work because Bizarro's biology is so warped that Kryptonite doesn't work on him.