[[quoteright:350:[[Franchise/{{Superman}} http://static.tvtropes.org/pmwiki/pub/images/superman_kryptonite11_138.jpg]]]]
[[caption-width-right:350:"Hey Superman, check out this awesome glowing rock I found! ...Supes? You okay?"]]

->''"Likewise, in fiction, whatever power a character has must have a downside somewhere, or he becomes a boring Superman type of character who can handle anything and get out of any difficulty, and he won't interest readers for long."''
-->-- '''Creator/TimothyZahn'''

The Kryptonite Factor is an AchillesHeel, where the weakness is a substance or state that only affects the SuperHero. It serves a few purposes.

The artistic one is to show that no one is [[InvincibleHero invulnerable]], not even our [[SuperpowerLottery godlike main character]]. This is especially ironic if the vulnerability is [[WeaksauceWeakness completely arbitrary and commonplace.]]

The more powerful a character is, the more likely the Kryptonite Factor will be abused. Writers in particular tend to dislike immensely powerful characters with a single Kryptonite Factor, because not using it creates a [[DramaPreservingHandicap drama-destroying]] sense that the character is never under a serious threat. Conversely, working a rare Kryptonite Factor into the plot repeatedly can [[KryptoniteIsEverywhere seem even more contrived]].

The most obvious example is kryptonite, the bane of Superman regardless of how powerful he is being portrayed at the time. A literal [[GreenRocks green rock]], it seemed unusually abundant in supervillainous hands for being radioactive bits of a planet that exploded lightyears away. Many {{Elseworld}}s and spin offs to the Superman mythos include characters who are more resistant to kryptonite, but conveniently, not as strong.

See also KryptoniteRing, KryptoniteProofSuit and FightOffTheKryptonite. Contrast {{Depower}}, CrossMeltingAura and DramaPreservingHandicap. Related to WhyDidItHaveToBeSnakes. If the character is vulnerable to something comparatively mundane (and even non-threatening), that makes it a WeaksauceWeakness. When this trope turns up far more often than seems probable, see KryptoniteIsEverywhere. When this extends to having characters whose powers are nothing more than a Kryptonite Factor, you have a ManOfKryptonite.

Thanks to Franchise/{{Superman}} being a LongRunner, and PopCulturalOsmosis, a common bit of MemeticMutation is to refer to something you are particularly vulnerable to ([[BaconAddiction such as Bacon]]) as "My Kryptonite."

Not to be confused with ''Series/TheKryptonFactor''. Contrast LogicalWeakness, wherein the weakness logically comes about as a direct result of the powers. ByThePowerOfGrayskull is more or less the opposite, giving powers as opposed to taking them away.


[[folder:Anime & Manga]]
* In ''Manga/FairyTail'', Natsu is a very powerful mage who often defeats his opponents handily. He, however, is completely incapacitated by motion sickness when on any mode of transportation (including piggy backs). This was even actively weaponized against him at times, such as when a villain lured him into a shallow river and rigged a raft from underneath his feet, instantly bringing him to his knees.
** This weakness of his is at least partially a psychological one, as he only falls ill on anything that he ''believes'' to be transport. Thus, since he doesn't consider Happy the cat to be transport, he can fly with him.
** It turns out that all Dragonslayers eventually develop this weakness.
** Wendy has this in the form of sour foods, like dried plums. She was once defeated simply by ''watching'' someone eating dried plums.
* ''Manga/InuYasha'':
** Inuyasha temporarily loses all of his demon-powers on nights with a new moon.
** There's also Miroku, who has a miniature black hole that is initially a game breaker. So the show introduces poisonous wasps which can kill him if he sucks them up. These practically become the villain's trademark so that only Inuyasha can be a credible threat to him.
* In [[Anime/FullMetalAlchemist the 2003 anime version]] of ''Manga/FullmetalAlchemist'', the homunculi become vulnerable when [[spoiler: they come into close proximity to the body of the human of whom they are a ShadowArchetype.]]
* In ''Manga/OnePiece'', anyone who has eaten a Devil Fruit has two, related Kryponite Factors: The ocean, which causes power leeching and an inability to move due to weakness, and Seastone, also known as ''Kairouseki'' or as "Sea Prism Stone", which replicates the effects of the ocean and out of which most prisons in the ''One Piece'' world are built.
** The effect of Seastone and the sea itself varies from user to user: Luffy (a paramecia user) and Chopper (a zoan user) have severe and painful reactions to either but are still made of rubber (which is used to save his life when he's drowning in the ocean) and a human-zoan respectively while logia fruit users and other paramecia users are simply unable to use their powers
** Smoker also has some Kairouseki on the end of his jotte, despite his being a fruit user himself (the weapon is long enough to keep him from coming into direct contact with the stone).
** Often applies with individual Devil Fruit in a sort of insanely complicated, poorly understood ElementalRockPaperScissors, particularly Logia. As an example, the fact that Luffy is a RubberMan allowed him to totally break the normal SortingAlgorithmOfEvil by easily defeating [[PsychoElectro Enel]], whose electric power was like unto a PhysicalGod.
** The Yami Yami no Mi also appears to act as kyrptonite to devil fruit users and seems to have been built just to combat them: of the 3 abilities shown so far; creating black holes (and expelling anything pulled in), pulling in devil fruit users and canceling fruit powers only the first can be used on normal people.
** Busoushoku no Haki (Armament Haki) allows the person who use it to surround himself/herself with a thin air but powerful armor (it's mostly invisible until the TimeSkip), allowing the user to negate devil fruit powers by contact. It does not cancel the devil fruit power itself, but it's one of the few only methods to attack and hurt logia-types. Trained Haki users can use their Busoushoku Haki for their projectile weapons or devil fruit powers.
* In ''Manga/DragonBall'', the main protagonist Goku severely weakens when he does not eat for long periods of time. Also, his original race, the Saiyans, usually posses a common weakness; if their tail is pulled, they will be rendered completely immobile. However, the Saiyans ability to adapt in battle allows them to adapt this weakness away so it is not that significant.
** In fact, in ''Dragon Ball Z'', this weakness is only ever successfully exploited in a single episode. It is only ever tried one other time, and never used or mentioned again.
*** In ''Dragon Ball'', Goku eventually toughened up his tail by constant training (before eventually losing the tail permanently). One presumes that Vegeta and Nappa had done the same.
* ''{{Franchise/Anpanman}}'' has a head made of bread, which is his weak point. If he breaks of too many pieces of it to feed others, or his head gets wet, dirty, bruised up, or moldy, he loses his power. Once a new head is put on, he gains all the energy he needs again.
* In ''LightNovel/ACertainMagicalIndex'', Saints are people [[BornWinner born]] with physically perfect bodies similar to the Son of God. This gives them great powers like incredible levels of SuperStrength, SuperSpeed, SuperToughness, etc. However, they are vulnerable to any of the tools that were used to torture Jesus. For example, if an ordinary person punched them or hit them with a baseball bat, they could easily shrug it off. But if a Saint was hit with a cross, crown of thorns, scourging whip, etc, the item would hurt them like it would a normal person. There are also spells designed to combat Saints, like the appropriately named "Saint Destroyer".
* In ''LightNovel/BlackBullet'', the monsters known as Gastrea are practically invulnerable to normal weapons, but weapons and bullets made of the metal Varanium can harm them, and monoliths made of Varanium can drive them away. However, there are Gastrea that are powerful enough to ignore the monoliths.
** Due to FantasticRacism in the series, it's been also used against [[WoobieSpecies cursed children]] who are born with the virus. [[spoiler: A group of cursed children that Rentaro taught were killed by a bomb filled with Varanium shards.]]

[[folder:Comic Books]]
* {{Franchise/Superman}} is the TropeNamer of course, with his weakness to Kryptonite (radioactive GreenRocks from his home planet) established back in the 40's. Since then, he's gained a few other vulnerabilities: he has only basic resistance to magic ([[DependingOnTheWriter though some authors treat magic as a bona fide weakness for him and his kin]]), red sun radiation can temporarily rob him of his powers, and there's a whole spectrum of coloured Kryptonite with varying effects (from Red Kryptonite that causes a random change for 48 hours, to Gold Kryptonite that robs him of his powers ''permanently''). He can be killed by a huge amount of brute force, as seen during The Death Of Superman, though of course he turns out to be OnlyMostlyDead.
** Of course, Doomsday was also ''from'' Krypton, leaving the reader to wonder if that gave him some sort of edge over the Man of Steel[[note]]the canonical answer is "no". It was mostly due to the fact that the fight dragged out into the middle of the night; without a source of solar radiation to replenish his powers and heal injuries, Superman just ran out of juice[[/note]].
** The Gold Kryptonite part is now "powerless for 30 seconds", mostly so it wouldn't be overused.
** He even has at least three villains -- Metallo, Conduit, and [[ManOfKryptonite the Kryptonite Man]] -- possessing powers that boil down to ''being Kryptonite.'' And now that Gold K has been {{Nerf}}ed, minor villain Radion has been revised into this as well.
** Ironically, Superman is infamous for [[FightOffTheKryptonite ignoring Kryptonite]] through sheer HeroicWillpower. The only thing he is always shown as vulnerable to is magic. This has proven a loophole to give [[{{Shazam}} Captain Marvel]] a [[SuperHeroSpeciation a firm place]] in TheDCU as a valuable ally for the Man of Steel.
** Superman also had problems with Red Kryptonite, special kryptonite that could randomly alter Superman's powers, doing anything from making his hair grow to actually slowly killing him.
*** In fact, Brainiac once used a special mix of red and green Kryptonite that gave him a third eye in the back of his head. In order to protect his secret identity, Supes pretended that the kryptonite had addled his brain to make him wear whatever hat is near him.
** Green, gold, and red kryptonite are only the tip of the iceberg. There are [[http://en.wikipedia.org/wiki/Kryptonite#Variations more colors of kryptonite than you can shake a stick at]], each with its own effects -- including "pink kryptonite", which can turn Superman gay (!).
* One ComicBook/{{Superboy}} story had him meet Mon-El, an amnesiac with powers like his, who assumed due to this that he was Kryptonian. Near the end of the story, Clark gets suspicious and lobs lead boulders painted to look like Kryptonite at him. Mon-El collapses, and Superboy flies in to accuse him of fakery -- but the trauma has [[EasyAmnesia brought his memory back]]; he's a Daxamite, a member of a race similar to Kryptonians, but with a weakness to lead poisoning instead of Kryptonite. To keep him from dying, Superboy puts him in the PhantomZone, preserving him for a thousand years until the ComicBook/{{Legion of Super-Heroes}} finds a cure.
** Later retellings have Clark and Mon-El seeing if Mon-El was a Kryptonian (whose memories were slowly coming back) and Mon-El getting sick after Clark takes out a lead box containing some Kryptonite, mostly so it doesn't [[SuperDickery make Superboy look like a massive dick]].
* The color yellow was/is a major weakness to the [[Franchise/GreenLantern Green Lantern Corps]]. This was eventually [[RetCon explained]] by the influence of a fear demon the creators of the rings had entrapped corrupting their powers, but also authorically served to constantly remind them their potential godlike power has limits (a GreenLanternRing being otherwise limited only by the intelligence, creativity, and willpower of the wielder). When Kyle Rayner was the only Green Lantern, thanks to Hal Jordan's BrainwashedAndCrazy FaceHeelTurn, his ring had no vulnerability to yellow. However, when Hal was brought BackFromTheDead and the four Earth Lanterns took down Paralax, the Entity of Fear (and thus, the Yellow Impurity that prevented Lanterns from harming yellow objects), it was reinstated and {{Ret Con}}ned that Lanterns can overcome the weakness by recognizing fear.
** Alan Scott, the [[UsefulNotes/TheGoldenAgeOfComicBooks Golden Age]] Green Lantern, had no vulnerability to yellow, but a similar vulnerability to wood. This was due to his more magical ring being connected to "green, growing things".
*** This was [[RetCon retconned]] into a long story involving one of Earth's first [=GLs=]. He was mad with power, so the Guardians gave him the wood weakness so primitive humans could club him to death. However, instead of dying, he put his soul into the power ring and battery, which collided with a Meteorite, becoming the Starheart. Alan Scott got his ring from the Starheart. Seriously.
*** The entire 'wood weakness' may have been a RetCon itself; some of the earliest comics indicate he has 'invulnerability to metal' but not really anything else, allowing him to be, among other things, knocked unconscious by a teak vase.
** It's worth noting however that because of this on-again/off-again vulnerability, the fact that Sinestro always has a yellow power ring is almost a GrandfatherClause.
*** Not quite. He was assumed to be dead while the fear entity was out doing whatever fear entities do.
** In the ''Elseworlds'' storyline ''ComicBook/SupermanAndBatmanGenerations'', it was revealed that the yellow vulnerability was just a hoax made up by the Guardians to keep the Green Lanterns from getting too cocky. Alan Scott's wood weakness, however, was psychosomatic and imposed by himself; during his early adventures, while fighting some ruffians, one snuck up behind him and hit him with a wooden club. While the truth was that he just didn't pay attention and thus allowed the foe to get in a cheap shot, he instead convinced himself that he had a weakness to the wood and thus couldn't defend himself. Guess he had a bit of an ego going...
** The Blue Lanterns are a bit different. Instead of having a weakness to another color, the Blue Lanterns are dependent on another color, namely green, in order to use their powers effectively. This is because green is the color of willpower and blue is the color of hope. You can hope all day long that something good will happen, but that won't accomplish anything unless you also have the will to help your hopes come true.
* The ComicBook/MartianManhunter (who is both powerful and has a variety of useful powers) has a vulnerability to fire. And a rather powerful addiction to cream-filled cookies, though this is more a comedic device. (See 2000's ''Martian Manhunter'' #24). In UsefulNotes/TheSilverAgeOfComicBooks, fire was treated by him as equivalent to Superman versus kryptonite, but ComicBook/PostCrisis, it became more of a crippling phobia. (They seem to keep going back and forth on this one.)
** At least once, his fire vulnerability was explained by saying that he almost died in a fire once, and has feared it ever since. This falls apart when one considered that ''every'' Martian who's ever appeared in Creator/DCComics has been vulnerable to fire. Current canon is that it's a genetic block implanted by the Guardians to [[SealedEvilInACan lock away]] the [[SuperpoweredEvilSide burning Martians]].
* Early versions of Franchise/WonderWoman had her lose her powers if she was tied up by a man, under "Aphrodite's Law", leading to some [[DoesThisRemindYouOfAnything bondage imagery]] that must have been blatant even at the time of its introduction. As noted in her entry, that was quite deliberate. In UsefulNotes/TheSilverAgeOfComicBooks, she went into an UnstoppableRage if her bracelets were removed. Currently, Wonder Woman has no Kryptonite Factor weaknesses.
** Partly because she is not as invulnerable as Superman or Manhunter. Bullets can penetrate her skin if she doesn't block them with her bracers and she needs to breathe, just as examples.
** She does (or at least did - her continuity is a moving target) lose her powers when she changes back to her secret identity, thanks to a spell cast by her ArchNemesis Circe. Which [[FridgeLogic raises the question]] of why she ever turns back to her secret identity, given that they look exactly the same. The only possible benefit to transforming is that it saves her the trouble of changing clothes.
** In one story (as in, within the past 10 years - not exactly yesterday, but well after ComicBook/CrisisOnInfiniteEarths) story, Batman defeated an Amazon footsoldier by throwing a magnetic baterang at her, which stuck her bracelets together when she blocked it and removed her powers. Suggesting both that the weakness is common to all Amazons, and that it survived into the modern age ... or possibly that whoever wrote that story was [[DependingOnTheWriter taking a few liberties]].
*** This was actually used in one of the incarnations of ''WesternAnimation/{{Superfriends}}'' - Scarecrow had captured Wonder Woman and Robin in an attempt to lure Batman into a trap. When Bats arrived, Wonder Woman had her bracelets fused together, thus rendered powerless.
* In ''ComicBook/{{Preacher}}'', Jesse Custer's power of [[CompellingVoice the Word]] (his ability to force people to do what he says) has a catch: the Word must be both ''heard'' and ''understood'' to work. Among other things, this means it doesn't work on animals, various characters avoid it by covering their ears, and at one point it's rendered moot when a squad of soldiers who only speak French are sent after him.
* In ''ComicBook/XMen'', ComicBook/{{Cyclops}}' optic blasts can be entirely contained by even a thin sheet of ruby-quartz (and, uh, [[RequiredSecondaryPowers his eyelids]] apparently) This is used to his ''advantage'', as he can't normally control his optic blasts at all, and so wears glasses with lenses made of the material. Occasionally a villain will strap some ruby-quartz armor, or lock a quartz helmet on to Cyclops's head, but usually they prefer to go the route of knocking off the glasses.
** His brother Alex is also immune to his powers, as is he to Alex's. This is explicitly a result of the shared RequiredSecondaryPowers that stop them from blowing themselves up.
* ComicBook/{{Wolverine}}, X-23 and some other fast healers in Marvel, have trouble healing when having "strange (or foreign) metals (or substances)" on their composition (such as Wolverine's adamantium skeleton, or being struck by carbonium) and thus not heal as fast (read: instantly)
* The ComicBook/NewGods of the DCU, while far from completely invincible (with the exceptions of the stronger ones like Darkseid) are ''all'' vulnerable to the very rare element Radion. In ''ComicBook/FinalCrisis'' [[spoiler: Darkseid kills his son Orion with a time traveling Radion bullet. Batman later fires the same bullet into Darkseid to fatally poison him; an act that eventually leads to Darkseid's FinalDeath.]]
* Common vulnerability of aquatic superheroes like Comicbook/{{Aquaman}} and the ComicBook/SubMariner is the need to remain hydrated (moreso than a normal person, that is). Generally, it's relatively mild - the need to be submerged in water at least once every 24 hours, for example - and comes up more as a way for villains to keep them prisoner than as something they need to worry about on a regular basis, but it does make them extra vulnerable to villains with heat-based powers, and a CrazyPrepared villain will always find a way to exploit it (Aquaman was once made to be afraid of water, for instance).
** Aquaman's hydrophobia is especially notable because it was brought about by Batman. That was one of the stories that solidified his status as CrazyPrepared.
* There is a certain gas that can remove ComicBook/SpiderMan's SpiderSense temporarily. It is often used by the goblin-based villains (Green Goblin, Hobgoblin etc.) or by Mysterio. Venom and Carnage are completely immune to the sense altogether, since their powers come from the alien suit Spider-Man wore. Removing his spider sense or being immune to it is always shown to be disastrous for Spider-Man. For instance, his Aunt May is immune to his spider-sense due to being a trusted family member. Trying to get to his bedroom, he snuck into her house one night, still dressed as Spider-Man. She managed to sneak up on him and ended up whacking him over the head with a vase, [[OldShame KOing him.]]
** One of the plot points in ComicBook/SpiderIsland was Peter temporarily losing his SpiderSense and realizing just how much he depended on it. He spent some time training with [[ComicBook/ImmortalIronFist Iron Fist]] to become less reliant on it.
* Inverted with [[ComicBook/{{New52}} The New 52]] version of Ultraman. He gets stronger by consuming kryptonite. However, ''[[WeakenedByTheLight sunlight]]'' weakens him. To counter this, he creates a solar eclipse after being amped up on kryptonite.
* In ''ComicBook/{{PS238}}'', Superman-CaptainErsatz Atlas is vulnerable to Argonite, the irradiated remnants of his homeworld Argos. [[spoiler:It later transpires that Argonite is a synthetic, Earth-made material created by the US military specifically as a way to keep Atlas in check. It also has the side-effect of working on ''all'' {{Flying Brick}}s, including native Earth ones like 84 and also every member of the not-at-all-destroyed Argos' noble houses.]]

* ''Fanfic/LastChildOfKrypton'': Revealed when [[spoiler:Gendo pulls a piece of kryptonite out on Shinji -who is Superman in this crossover- after the Bardiel incident.]]
* ''Fanfic/SOE2LoneHeirOfKrypton'': Asuka discovered she was half-kryptonian at the same time she found out about her weakness towards kryptonite. Shortly after [[spoiler:Gendo stole the piece of kryptonite and he threatened her with it several times.]]
* A ''Franchise/StarWars'' version here ''[[https://m.fanfiction.net/s/7034896/1/ The Princess And The Pirate]]''. The Imperial-aligned captors of Luke, Leia and Han put them in a room with some kind of small, furry mammalian creatures that somehow sap the two Force users' power and prevent them breaking out. Luke eventually solves the problem by killing them. However, it accidentally happens again later, when a young rebel thinks Leia would like one of the cute critters and lets it loose. Leia faints, but Luke's able to tell him to get it out of the area.
* In ''Fanfic/PonyPOVSeries'', a Draconequus like Discord and his family are all {{Reality Warper}}s. However, they cannot directly affect anything created by taking away something. For example: ice (created by taking away heat), despair (created by taking away hope), and the vacuum of space (created by taking away air and matter). As a result, they can be imprisoned by ice and similar substances for a time (note that although they cannot poof away ice or transmute it, they can eventually generate enough heat to melt it or break free with brute force). They are also vulnerable to the Rainbow of Light and its present day counterpart the Elements of Harmony.

* The title character of ''Disney/{{Bolt}}'' is a dog on a TV show who thinks his superpowers are real. When he is accidentally placed in a box and shipped to New York, he finds that he no longer has superpowers, and thinks the Styrofoam peanuts in the box are the cause of it.
* Franchise/{{Godzilla}}, in the film ''Film/GodzillaVsBiollante'' is revealed to be weakened by the [[FunWithAcronyms ANB (AKA The "Anti-Nuclear Bacteria").]] Though, for some odd reason, it's ''never used again'' in later films.
* Lampshaded in ''Film/{{Unbreakable}}''. David is a horrible swimmer and nearly drowned once as a kid. Discovering this was evidence reinforcing that he ''was'' actually "unbreakable" because all heroes have some sort of weakness. Another character points it out to him, saying "that's your Kryptonite."
* In a dream sequence in ''Film/HaroldAndKumarGoToWhiteCastle'' (aka ''H&K Get the Munchies''), the bullying sheriff gets to say this terrific line after he gets shot: "Bullets! My only weakness! How did you know?"
* In ''Film/WhoFramedRogerRabbit'', Toons are invulnerable to conventional damage, but can be injured or killed by a specific blend of paint-and-ink-thinning chemicals, known as "the Dip". Immersion is fatal, and a Toon cab who'd skidded through a puddle of Dip suffered four flat tires and was left limping in pain.
** They also can't let the ol' "Shave and a Haircut - Two Bits" go unfinished. Roger ends up ruining their hiding spot because of it.
* Lampshaded in ''Film/SkyHigh'' - instead of arbitrary medical checkups, students are exposed to GreenRocks of different colors to check for weaknesses.
* All superheroes in ''Film/UpUpAndAway'' are weakened by ''tin foil''. Too much is fatal. When the main character's friend brings over a meal that's wrapped in foil, the parents (all supers) treat it as a bomb and then bury it in the yard. Of course, the BigBad finds out about this and then goes to the nearest grocery store.
* In ''WesternAnimation/MegaMind'', the eponymous villain accidentally defeats Metroman by trapping him in a room lined with copper, his previously unknown weakness. [[spoiler:It turns out to be a trick to allow Metroman to fake his own death]].
* Lampooned in-character in ''Film/TheAmazingSpiderMan'', when Spider-Man responds to a crook pulling a knife by [[LargeHam melodramatically pretending to collapse]] and gasping "You've discovered my weakness... small knives!".
* ''Film/ManOfSteel'':
** Exposure to Krypton's native environmental conditions weaken and at first even incapacitate Superman.
** Zod's Kryptonians similarly initially lose control of their powers and pass out while trying to adapt to Earth's native atmosphere.
* In ''Film/LemonadeJoe'', Joe is a strong, tough guy with ImprobableAimingSkills. There is one substance that is his Achilles Heel and makes him lose consciousness, leaving him at his enemies' mercy. It's alcohol.
* In ''Film/DraculaUntold'', vampires have the standard array of weaknesses: silver, sunlight, wooden stakes, and crosses. Also played with a bit. Crosses only work on permanent vampires, the ones that have fed on humans. Those like Vlad, who will turn back in three days, are unaffected. Stakes, on the other hand, are not only effective but ridiculously so; when Mehmet goes after Vlad with a stake, his armor actually evaporates around it so the stake will hit flesh.

* The Alteriens of Adam R. Brown's ''{{Literature/Alterien}}'' are pretty powerful, but they too have their weaknesses. Iron objects can hurt Alteriens, going so far as cancelling out their ability to absorb kinetic energy. As such, an Alterien can be cut or even killed with iron. It is of note, however, that it takes far more than a cut to kill an Alterien. It would take the same amount of effort as it would for a human using an ordinary knife or sword. This means an Alterien can die if beheaded or cut in half by an iron blade or stabbed multiple times with iron to the point of overtaxing their healing factor. Alteriens such as Oberon are also vulnerable to areas of concentrated dark psychic energy. Whenever Oberon is in or near such an area, he becomes very weak and his ability to absorb energy is reduced.
* ''StarWars'' got in on the act in the ExpandedUniverse by having creatures who "pushed back" the Force (in the case of the ysalamiri), hunted ''with'' the Force (thereby making them far more aggressive around Force-users, as with the vornskrs), or who had been "severed" from the Force, and so were unable to be sensed or affected by the Force (like the Yuuzhan Vong). The idea, of course, was creating handicaps so that a simple kidnapping plot, for example, would work against Jedi, who would normally be able to shrug off drugs, sense someone walking up behind them, open locked doors, etc.
** Let's not forget the mighty lightsaber's weakness: the totally useless space-metal cortosis, which renders a lightsaber useless for a few seconds.
*** Oh and for most you can't immerse them in liquids without the blade switching off. Rain's fine though, and Jedi from water worlds fix this problem with some modifications.
** Lightsabers have another weakness as well. Bullet based weapons (called "slug throwers" in universe) can't be reflected by a lightsaber as blaster bolts can. All it does is melt the projectile, which means instead of a Jedi having a speeding bullet coming at their face, they have a piece of ''liquid metal'' coming at their face.
* Parodied by CaptainUnderpants, who ''thinks'' he loses his powers when he's sprayed with starch. It's actually a PlaceboEffect, because he only believes it because that's what George and Harold wrote in their comic book.
* ''Literature/TheDresdenFiles'': A lot of mythological monsters [[AllMythsAreTrue exist]] InUniverse, and they all have their mythological weaknesses. Some prominent examples;
** [[TheFairFolk Faeries]] have a crippling weakness to iron. It burns them on contact, and even mortals bestowed with their power (the summer and winter knights) lose it on contact with iron.
** The White Court of Vampires are burned on contact with the the emotion opposite to what they [[EmotionEater feed on]]. House Raith, for example, feed on [[HornyDevils lust]], and their weakness is [[ThePowerOfLove love]].
** Wizards aren't able to channel magic through or over large amounts of water, especially running water. A villain once tied Harry up and kept him under a cold shower, rendering him helpless.
*** Harry once got around this by swimming to the bottom of the lake he and his friends were about to drown in, sticking his hand in the mud at the bottom, and casting magic that way.
*** [[WordOfGod Word of Jim]] is that [[MagicalNativeAmerican Listens-to-Winds]] can use magic despite the presence of large amounts of water, due to being a extremely powerful [[MakingASplash hydro]][[{{Main/Whatevermancy}} mancer.]]
* Crucial in ''{{Steelheart}}'', where every super-powered "Epic" has a weakness that will either cancel out their powers or at the very least make them vulnerable to physical attack. Sometimes it's as straightforward as being close to a particular kind of metal, but others get crazier - like one who the characters mention could only be killed by people who are 37 years old.
** It's revealed in the second book that [[spoiler: an Epic's weakness is related to their greatest fears and traumas. Sourcefield, for example, is vulnerable to Kool-Aid because when she was human her grandparents tried to poison her with it. Megan almost died in a burning house when she was younger, and therefore became vulnerable to fire upon her transformation.]]
* In ''Literature/AfterTheGoldenAge'', Captain Olympus is a NighInvulnerable FlyingBrick, but he has one weakness: [[spoiler:the same radiation that originally gave him his powers]].
* In ''Literature/ASongOfIceAndFire'', [[UsefulNotes/{{Obsidian}} dragonglass]] is the main weakness of [[AnIcePerson the Others]]. Sam Tarly was able to kill one by stabbing it with a dragonglass dagger.
* In ''Literature/TheFalconer'', the traditional cold iron is useless against fairies. However, a special species of thistle is very effective. Which is why said thistle is nearly extinct. The fae were very diligent about that.

[[folder:Live Action TV]]
* Because the writers of ''Series/{{Smallville}}'' have small[ville] imaginations, they are unable to construe ways of having Clark Kent face danger without invariably introducing some form of the Kryptonite Factor. They did bring up Clark's vulnerability to magic but rarely use it because of how much one can stomach magic in a thematically sci fi show. This led to the GreenRocks factor exploding with Kryptonite being used for nearly every villain's plot so that it had some reason to be around, e.g. Kryptonite being needed to ''print money''.
** Although this formed a mutually JustifiedTrope with the Smallville MonsterOfTheWeek format. Kryptonite produced the baddie/misguided teen that Clark went up against each week and they were actually a challenge (it's hard to use your telepathy to cheat on midterms if Superboy had already punted your ass into the next county) because they were fueled by Kryptonite.
* Parodied on the Nickelodeon sketch comedy show ''Series/AllThat'', where recurring character Superdude's weakness was "lactose intolerance", meaning in his case that merely being in the proximity of dairy products was harmful to him. Naturally [[ThematicRoguesGallery all of his opponents were dairy themed]].
** Or would fight in an area where dairy products would be common. Such as a cow barn.
** Another All-That villain got his powers from radiative materials stored in a bucket that landed on his head. Problem was, he couldn't get the bucket off, and his blind attempts at heroism were often... [[DestructiveSaviour less than ideal]].
* Non-super example: James May of ''TopGear'' appears to have mild to moderate obsessive-compulsive disorder. His co-presenter Jeremy Clarkson once drove him offstage by rotating the bezel on his watch until it was out of alignment with the face
* In ''Series/DoctorWho'', the Doctor's sonic screwdriver was notorious for having no specific guidelines or limits to how it could be used, so much that lazier writers would rely on it too much as a DeusExMachina to get the Doctor out of any predicament. The Fifth Doctor broke it and went hands free. When the series returned in 2005, two very specific limitations were put on it: a), the screwdriver can't break through [[TechnoBabble a Deadlock Seal]], and b), [[WeaksauceWeakness "it doesn't do wood"]]. The latter has been repeatedly [[LampshadeHanging lampshaded]] as "rubbish".
* For Sportacus from ''Series/LazyTown'', it's [[WeaksauceWeakness sugar]]; eating any sugary food renders him immediately comatose, and fresh fruit ([[CriticalResearchFailure despite having a high sugar content]]) or vegetables (a classification that includes the Sugar Beet) are required to restore him.
* Cole on ''Series/{{Tracker}}'' was vulnerable to Lodestone - it interfered with his life force sensing ability and weakened him a bit.
* In ''Series/{{Supernatural}}'', salt can stop most monsters. Demons can not cross a line of salt. Ghosts are repelled by salt. Fairies have to count every grain of salt if it is spilled in front of them.
* In ''Series/{{Arrow}}'', people who've taken Mirikuru are almost unstoppable; bullets and arrows do nothing and they're strong enough to overpower anything. Their only apparent weakness seems to be explosives; even small ones tend to knock them out for a bit to deal with them. Somewhat downplayed, however, since explosions are likely to kill anyone, but its notably the only thing that's been able to deal with them more than once.

[[folder:Mythology, Folklore, and Religion]]
* The Chinese tale of the [[https://en.wikipedia.org/wiki/Ten_Brothers Ten Brothers]] has ten brothers all born with supernatural powers that they lose when they come into contact with limestone.
* Traditionally ColdIron (which may or may not be the same thing as regular iron) is this to TheFairFolk, serving both to drive them away (hanging an iron horseshoe over your door turns it into an [[InsurmountableWaistHighFence impenetrable barrier]] to them) as well as being directly harming them (they cannot physically touch iron without being harmed, and iron weapons are the only things capable of killing them)
* Over the centuries vampires have managed to accumulate a truly impressive list of traditional kryptonite factors (rivaled only by that of [[PunyEarthlings squishy humans]]), to the point that most writers have to {{nerf}} or outright ignore several of them [[OurVampiresAreDifferent to make vampires]] [[YourVampiresSuck pose any sort of threat]].
* The Norse god Balder was so greatly revered that every object, every element and every organism in the world [[IntrinsicVow vowed]] that it would never harm him, effectively making him invulnerable to everything... except for mistletoe, [[TemptingFate which was never required to make such a vow because it was thought to pose no threat]]. Three guesses as to how that turned out.

[[folder: Tabletop Games]]
* The ''TabletopGame/{{Ravenloft}}'' game setting's ''Van Richten's Guides'' not only expanded on a lot of creepy D&D monsters' powers, but also gave plenty of them unique Kryptonite Factors of their own. We're not talking about the usual garlic-vs-vampires stuff; in Ravenloft, even ''golems'' have their own personalized Kryptonite, which players have to figure out if they're going to use it against the baddies.
* Vulnerability and Weakness are used to represent this in ''{{GURPS}}''.
* A rather [[ScrappyMechanic spiteful]] example in [[TabletopGame/{{Warhammer 40000}} Warhammer 40k]] with the Grey Knights Space Marines, MagiTek SuperSoldiers that comprised the fighting arm of the Ordo Malleus, also called the [[ExactlyWhatItSaysOnTheTin Daemonhunters]]. Back in 3rd edition and earlier, Daemons were generally pretty rare but powerful shock troops that were small auxiliary subsets of other armies, like the Eldar with their Avatar and the Chaos Marines with their [[CaptainObvious Chaos Daemons]]. One usually wouldn't fight an all-daemon army, and if an all-daemon army ever was fielded (usually by the {{Munchkin}}, given that this was a major GameBreaker back in the day), it usually was by the player's choice. So if you spammed Daemons and came up against a Daemonhunter player, you were just getting your well-deserved comeuppance for fielding a cheap army. But then Games Workshop went and split the Chaos Marines from the Chaos Daemons into two separate books in [[WhatWereYouThinking one of the most maligned decisions in the history of the hobby]] (which is saying ''a lot!''), and suddenly you had an entire ''faction'' who fell prey to another army almost by virtue of [[WeaksauceWeakness the other army showing up]].
** As of April 2011, the Grey Knights themselves were given their own book to replace the Daemonhunters Codex. They're still insultingly effective against Daemons, [[{{Flanderization}} if not]] [[UpToEleven more so]]. They just got better against other armies.
*** Grey Knights have more or less became the EliteMook of the Imperial forces, rather than a dedicated Daemonhunting branch. However they still have a horrendous number of special rules against Daemons and it's even possible to ''statistically destroy 33% of a Daemon player's army'' before the game even starts, and that's without tailoring. Before these rules came with an additional rule that benefitted Daemons, to balance out the power. It's gone now.
* ''TabletopGame/MutantsAndMasterminds'' has the Vulnerability and Weakness drawbacks.
** The official adventure module, ''Time of Crisis'' adds a weakness to [[spoiler:the Big Bad Omega]] in the form of [[spoiler:the cosmic detonator rods you've been pulling from the various Cosmic bombs]] which will completely bypass all of his defenses, potentially turning the final battle into a [[CurbStompBattle curb stomp]].
* Essentially required of characters (including NPC monsters) with superhuman toughness and/or regeneration in ''TabletopGame/TheDresdenFiles''. ''Something'' -- referred to as "the catch" -- must exist that bypasses their defenses, and common and/or obvious catches can provide point cost breaks. (Obscure ones like [[spoiler:Nicodemus's vulnerability to his own Judas Noose]] are okay, too, it just means paying the full cost.)
* Given the origin of the trope, pretty much any superhero RPG of course has a version of it. ''TabletopGame/{{Champions}}'' for example provides both Vulnerability (where certain attacks are more effective) and Susceptibility (where just exposure to the offending factor is enough to cause ill effects), plus of course the option of applying Limitations to powers so they become cheaper but for example don't work under all circumstances or against certain things.
* Lead is extremely poisonous to Europans in ''TabletopGame/RocketAge''.

[[folder:Video Games]]
* MMORPG Example: In ''VideoGame/CityOfHeroes,'' one can unlock the "Kheldian" Epic Archetype, a form of EnergyBeings from outer space that have merged with humans. Though they possess a greater arsenal of powers than "ordinary" heroes, as well as the unique ability of shapeshifting, they also possess a fatal weakness to a particular form of [[PureEnergy Quantum Energy]]. Thus, while playing or teaming with one, enemies wielding Quantum Array Guns are mixed in randomly with the ordinary enemies -- as are the lethal "Void Hunters", mercenaries specifically trained to hunt and kill Kheldians, adding implants that protect them from Kheldian attacks to their Quantum Array Guns.
** This weakness was toned down due to years of player complaints as the Quantum Weapons were considered to be too commonplace for such a powerful attack. Now the quantum weapons deal less damage and only stun the player for a fraction of a second rather than taking over a third of their life and leaving them stunned for too long to defend themselves.
** Having a Kheldian on the team will occasionally spawn [[DemonicSpiders Shadow Cysts]] that spawn spirits that ruin accuracy and attack speed of everyone on the team. Oh, and they explode when destroyed. And they're surrounded by Mooks who will probably kill you because you can't aim or fight back. For the most part, Shadow Cyst = TotalPartyKill. Thanks Kheldians!
** To add insult to injury, Kheldians aren't really particularly overpowered. They're actually pretty lackluster in comparison to the other archetypes, at least without a whole lot of work and expense tricking out your build.
* Haar in ''Franchise/FireEmblem 10'' is an otherwise OneManArmy mechanically, but (also mechanically) is pretty much always 2 hit killed by thunder mages.
** This applies to almost every unit with a weakness in the FireEmblem games: Attacks with a weapon the target is weak to (this is distinct from the sword>axe>lance>sword thing) triples the weapon's "might" stat. And pray you don't get unlucky enough to get hit by a critical hit by your weakness.
* In ''VisualNovel/TearsToTiara'' and the sequel ''[[VideoGame/TearsToTiara2 Tears to Tiara 2]]'', non-humans on your team are effected whenever the bad guys use Obelisk to unleash the "holy" aura Gravitas.
* ''VideoGame/{{Runescape}}'' lets you create Kryptonite in the form of Bane Ore. This stuff can be tuned to various creatures, and doing so will make it harmful to them. Bane Metal can then be made into arrows and bolts. Balmung, the axe you use to slay [[SeaMonster Dagganoths]] during a difficult quest, is revealed to be made of Bane Metal as well.
** The Vampyre Quest series brings us Silverthril, an alloy of mithril and silver, which is somewhat effective at slaying immortal Vyrewatch. Later on, weapons crafted from the Blisterwood Tree take this UpToEleven.
* In VideoGames/{{Scribblenauts}}, a few creatures are impossible to kill except using some special objects:
** Vampires can only be harmed by crosses, stakes, garlic, sunlight and anything with the adjective Holy. Using any of those will instantly slay the vampire (yes, even throwing a clove of garlic to him), but there are useless or very weak weapons against any other foe.
** Ooze [[KillItWithFire can only be killed with fire]]

* Aberration in ''Webcomic/ElGoonishShive'' are difficult to harm using physical attacks, but are weak against magical weapons, to the extent that a HyperspaceMallet not normally capable of causing any real harm becomes a useful weapon against them.

[[folder:Web Original]]
* In the superhero spoof AdventureGame ''The Frenetic Five versus Strum und Drang'', the character Pastiche has various powers, the most notable of which is an ability to become an IntangibleMan (woman). Her only weakness: she can't phase through ''[[BoundAndGagged rope]]''.
* In ''Literature/TalesOfMU'', the half-demon Mackenzie may be partially invulnerable, but crossing yourself is the only thing needed to repel her. In peoples of faith, this actually ''pushes'' her away and causes unbearable pain.
* Incredibly powerful mage Fey in the WhateleyUniverse is indeed one of TheFairFolk, and so she has a weakness to cold iron. And synthetics, which give her really nasty rashes. She has wardrobe problems because of that one.
** Anyone who is able to use Erebeal Magic (one of the forms of CastingAShadow in-universe) develops a negative reaction to the herb moly. Nacht, who was [[spoiler: [[AbusiveParents dipped into the Erebos as an infant and not expected to survive]], but did]], has this to a crippling degree, but fortunately for her, ''real'' sacred moly is exceedingly rare.
** Played with by Phase, who's managed to slip a ''fake'' Kryptonite Factor into her official file. For the record, it's [[spoiler:"dark chocolate administered orally"]].
* Upon entering melee range of any anti-dragon Noble Phantasm, Uther from ''Roleplay/FateNuovoGuerra'' suffers a rank-down for all of his stats, in addition to any damage bonuses they have against him.
* Fidget, a KidHero speedster from the ''Roleplay/GlobalGuardiansPBEMUniverse'', takes actual physical damage if you tie him down and prevent him from moving. If you stop him from moving, his power literally builds up and starts vibrating his cells to pieces.
* Going along with being an {{Expy}} of {{Franchise/Superman}}, Splendid from ''WebAnimation/HappyTreeFriends'' has kryptonut in one episode, which is basically kryptonite shaped as an acorn. Exposure to the radiation from it causes him to lose his powers and fall ill with what resembles the stomach flu. At the end of the episode, he crushes the kryptonut and accidentally inhales the powder, causing him to vomit uncontrollably as the skin on his face falls off. This (and another instance confirmed by WordOfGod) is the only time he has ever died, as nothing else can hurt him.

[[folder:Western Animation]]
* Interestingly, in ''WesternAnimation/SupermanTheAnimatedSeries'', it was originally planned that Supergirl, being in this iteration not from Krypton, but rather the sister-planet of Argos, would not have a weakness to Kryptonite. By the time of ''WesternAnimation/JusticeLeagueUnlimited'', though, the weakness was firmly in place.
* Spoofed in an episode of ''WesternAnimation/{{Freakazoid}}'', in which bad guy Guttierez tries presenting a variety of weaknesses (the color yellow, water, and kryptonite itself), failing each time, as Freakazoid points out that that's some other iconic character's weakness.
** Freakazoid himself has two rather obscure and ridiculous weaknesses, though: he can be imprisoned in a cage with graphite bars charged with negative ions, and he has an aversion to "poo gas".
---> '''Freakazoid:''' Dumb, dumb, dumb! Never tell the villain how to trap you in a cage!\\
'''Guttierez:''' You probably shouldn't have helped us build it, either.\\
'''Freakazoid:''' I know! Dumb!
*** Though as Guttierez pointed out, no one likes "poo gas".
* CaptainPlanet has a very odd weakness in that it's pollution, the very thing he's trying to fight. It'd be like Superman deciding to specialize solely on kryptonite cleanup duty.
** His EvilCounterpart Captain Pollution, is weak against pure wind, water, earth, and fire while being composed of concentrated pollution. This makes it interesting in that they're literally walking kryptonite to one another.
*** Captain Planet was also shown to be weak to intense hatred in at least one episode. UsefulNotes/AdolfHitler managed to completely disable him just by ''glaring'' at him. However, hate is regularly shown to be the pollution for ''Heart'' as even one of the rings used to summon Captain Pollution was Hate which was the negative copy of the Heart ring.
* In a BadFuture segment on ''WesternAnimation/TheGrimAdventuresOfBillyAndMandy'', rebels led by Irwin use frogs as weapons, as they've learned that they are giant worm/planetary tyrant Future Mandy's Kryptonite Factor. [[spoiler:They're wrong, as Mandy had leaked that information herself.]]
* In an episode of ''WesternAnimation/TinyToonAdventures'' spoofing the ''Film/{{Superman}}'' movies, "Super-Babs" was weak to carrot cake -- she couldn't stop eating it, and the villain continued feeding it to her until she was too overweight to fly after him.
* The ''WesternAnimation/JusticeLeague'' cartoon downplayed or ignored the Kryptonite Factor of every character ''except'' Superman. Franchise/GreenLantern's vulnerability to yellow was never actually mentioned (though occasionally, if you watch closely, you'll see yellow stuff getting through his force barricades). [[ComicBook/MartianManhunter J'onn J'onnz]] had no particular vulnerability or [[WhyDidItHaveToBeSnakes phobia]] regarding fire (though he had a bad case of TheWorfEffect in the first season, and he would occasionally struggle in situations where there was a lot of fire). {{ComicBook/Aquaman}} never seemed overly discomfited by being out of water for extended periods. Franchise/WonderWoman... well, she'd lost most of her Kryptonite Factors by the time the series started anyway. Hawkgirl eventually ''gained'' a Kryptonite Factor that was more emotional than physical and ended up resolved by series end anyway. TheFlash almost never used his powers to their full extent (not unlike Superman), with the idea that he never really pushed himself to excel...and when he did, he was given a convenient excuse not to again. {{Franchise/Batman}}'s "Kryptonite Factor"--that he was a perfectly mortal human--came up time and again, but, [[MemeticBadass being Batman]], doesn't really count.
** When ComicBook/LexLuthor was in the body of The Flash ("The Great Brain Robbery"), he took down Green Lantern with a cup of (yellow) pudding.
** Fair enough, though, they used the weaknesses against Amazo, particularly Kryptonite.
** Heroes actually abused this, by having Martian Manhunter pretend to be Superman in front of Lex Luther to get a confession for a crime.
* The ''WesternAnimation/ThunderCats'' are vulnerable to "thundranium", a rare mineral that is pretty much a poorly-disguised knock-off of kryptonite.
* In the ''WesternAnimation/TeenTitans'' cartoon, Starfire is allergic to metallic chromium. The allergy is more dangerous to others than herself, as it causes her to sneeze energy blasts. It even turns out to be an advantage, as it allows the team to track a chromium-based bomb. It's also a big case of artistic license, as chromium is used in a lot of common technologies.
* Imaginary Man, a superhero imaginary friend on ''WesternAnimation/FostersHomeForImaginaryFriends'', is weakened by girly things, particularly flowers. Similarly, his evil nemesis Nemesis, loses her powers whenever her hair is messed up. It later turns out they were thought up by a boy and his sister, respectively, just to annoy each other.
* The SushiPack are weakened by heat, and since they have a tendency to announce it, their most recurrent villains usually keep a couple of heat lamps around.
* On ''WesternAnimation/TheMightyB'', Bessie (who fancied herself a would-be superhero) once tried to find her Kryptonite Factor by going through every food item she could think of alphabetically. By the time she got to zucchini she was so full that she became violently ill, and thus thought that zucchini was her weakness.
* In ''WesternAnimation/ThePowerpuffGirls'' the titular girls lose their powers if they come in contact with Antidote X.
* On ''WesternAnimation/BatmanTheBraveAndTheBold'', when Batman [[spoiler:received powers on the planet Zur-En-Arrh, the supervillain Rothul quickly figures out the new Superman-like Batman's weakness: Quartz.]]
* Parodied in a WesternAnimation/RobotChicken sketch when after a fireball destroys another enemy, it also melts half of Composite Santa's body.
-->'''Composite Santa:''' Temperatures over 32 degrees Fahrenheit! My only weakness!
** It is now essentially his catchphrase.
* The animated film ''WesternAnimation/SupermanDoomsday'' contains an almost amusing example in that even ''Superman'' needed Kryptonite to defeat his clone with identical powers. Admittedly, the real Superman isn't quite at full strength at this point.
--> '''Superman''': You have all my strengths... and weaknesses.
* Specifically parodied in one episode of the ''WesternAnimation/EarthwormJim'' animated series. Jim is helpless against the substance known as Wormtonite (which Peter Puppy claims they found at the back of the fridge, and might once have been cheese). Bizarrely, its effects include turning Jim into a bowl of candied corn.
* ComicBook/SpiderMan would occasionally make sly references to a "guy who's allergic to green rocks".
* Haggarium drains the power of Voltron in ''WesternAnimation/VoltronForce'', as well as its component lions.
* ''WesternAnimation/TheSimpsons'': Bart once discovered principal Skinner's allergy to peanuts, and used it to practically enslave him. Skinner soon learns that Bart has an allergy too; Shrimp. They end up in a "sword" fight with sticks with their opponent's kryptonite on the end.
* ''WesternAnimation/DannyPhantom'' is weakened by a flower called Blood Blossom. It removes his powers while causing him extreme pain. That's not to mention the various weapons his parents and Vlad have devised that can remove his powers or hurt him while he is intangible.
** Ectoranium, introduced in ther SeriesFinale, is a green glowing rock that ghosts can't touch without being painfully shocked; they can still phase through it, which is an important plot point. Kind of an obvious {{Expy}} of Kryptonite, but in this case the Ectoranium is as much of a danger to humans as ghosts since it's a large asteroid that got knocked off course towards Earth.
* ''WesternAnimation/WordGirl'' loses her powers and gift of perfect vocabulary when exposed to lexonite, a radioactive mineral from her home planet.
* The 1987 version of ''[[WesternAnimation/TeenageMutantNinjaTurtles1987 Teenage Mutant Ninja Turtles]]'' parodied this in the episode "Michelangelo Meets Bug Man". In it, Michelangelo finds Bug Man, who turned into the superhero when he got angry, wrapped in chains that were laced with his main weakness before being thrown down into the sewer. His weakness? "Leestanite"! [[note]]The name is not an accident: it was a play on famous comic book creator Creator/StanLee.[[/note]]
* In ''WesternAnimation/MyLittlePonyAndFriends'', Grogar is incredibly powerful and seemingly nothing can hurt him, but once a certain bell is rung, he is automatically banished back to the Shadow World.
* In ''WesternAnimation/AvatarTheLastAirbender'', earthbenders can't bend metal (until Toph discovers how). In ''WesternAnimation/TheLegendOfKorra'', metalbending techniques have become widespread, so the new kryptonite is platinum. Metalbending works by bending impurities within the metal, and platinum doesn't have enough impurities to bend.

[[folder:Real Life]]
* [[http://blogs.discovermagazine.com/notrocketscience/2011/03/29/why-is-aspirin-toxic-to-cats/ Aspirin is kryptonite to cats]]. This article even acknowledges the trope.
* Chocolate to canines.
* While it is much less known, chocolate is dangerous for cats too, though cats are much less likely to eat it than dogs are.
* Any human with a severe food allergy. Peanuts are a frequent culprit here, with some unlucky folks unable to be in the same room as peanut products without going into respiratory shock.
** Diabetics have an even worse reaction to sugar.
* Salt to snails/slugs.
* Freshwater fish in saltwater and vice versa due to osmosis.
* The New England Patriots and Bernard Pollard. Pollard has destroyed the Patriots so many times that his fan nickname is the "Anti Patriot" and the "Patriot Killer". Pollard is a good player and is generally well-regarded, but it's bizarre coincidence that Pollard has done the biggest damage to the Patriots.