History Main / TakesOneToKillOne

->''"Magic must defeat magic!"''

A subtrope of MutualDisadvantage. An opposite of TacticalRockPaperScissors where each type of combatant has some other capable of [[CurbStompBattle curb stomping]] it. However, this can be a subtrope of ElementalRockPaperScissors if an element happens to be weak against itself. Compare BeatThemAtTheirOwnGame, HoistByHisOwnPetard, and SummonBiggerFish. Contrast LikeCannotCutLike and CounterpartArtifacts.

* ''Ninja 3: The Domination''

* ''Franchise/MarvelCinematicUniverse''

* Franchise/DCExtendedUniverse:
** ''Film/ManOfSteel'': No one knows about kryptonite ([[Film/BatmanVSupermanDawnOfJustice yet]]), so the only one who's able to stop the rampaging Kryptonian General Zod is Superman, a Kryptonian himself, being strong enough to [[NeckSnap break Zod's neck]].
** ''Film/{{Wonder Woman|2017}}'': Diana was led to believe that the God-Killer, a legendary weapon forged by Zeus himself to slay other gods (specifically Ares) is a sword, which she steals while fleeing Themyscira to join the war. When she finally confronts Ares in battle, he easily destroys the sword, and reveals to her the truth: the only thing in the world that can kill a god is another god. The actual God-Killer is Diana herself, as the daughter of Zeus. And she ends up doing just that.
* The whole premise of ''Film/PacificRim'': "To fight monsters, we created monsters of our own." Or, in other words, the only thing that can kill a horde of colossal {{Kaiju}} (without massive collateral damage) is a legion of equally HumongousMecha.
* In ''Film/LeftForDead'', the only thing that can destroy the demonic ghost Mobius Lockhart are his own weapons: a pair of pistols he claims were forged in hellfire.
* ''Film/TransformersRevengeOfTheFallen:'' The Fallen is, as his name implies, a [[FallenHero Fallen Prime]]. It is said that only another Prime can kill him, and naturally Optimus is the only one left. Showing a high level of GenreSavvy, he refuses to engage Optimus, and simply stays in his base until Optimus has been killed. Once Optimus gets better (as Optimuses do), the Fallen ''still'' avoids getting close to him. [[spoiler:He doesn't engage Optimus until his plan has been foiled, by which point he has nothing left]].

-->-- '''Uncle''', ''WesternAnimation/JackieChanAdventures'', explaining for the umpteenth time why you [[DidYouJustPunchOutCthulhu just can't punch out Cthulhu]] [[JustShootHim or shoot him]]. [[WeakToMagic At least not without magic powers.]]

** Despite having two other weaknesses[[note]]Ice-type and Fairy-type moves.[[/note]], the Dragon-type is super effective against only one type due to their sheer strength: itself.

** The Dragon type is super effective against only one type: itself. [[note]]Though Dragon-types are also weak against Ice-type and Fairy-type moves.[[/note]]
** The Ghost type also has a weakness to itself, though it's vulnerable to a number of other types as well. Since Giratina and the Dreepy are both Ghost- and Dragon-type, they are often the best counter to themselves.

* The Mechon of ''VideoGame/XenobladeChronicles'' are all but immune to conventional weapons. However, weapons crafted from trashed Mechon parts can cut through their armor just fine.

* In ''Series/KamenRiderZiO'', the villainous [[EvilKnockoff Another Riders]] have ResurrectiveImmortality and can only be beaten permanently by the powers of the Rider they imitate. Unfortunately, their existence has the side effect of [[RetGone retconning the heroic Riders out of existence]]; fortunately, Zi-O's whole gimmick is PowerCopying. [[spoiler:Series/KamenRiderDecade could presumably also do the job, but he spends most of the series pretending to be evil as part of a StealthMentor act.]] In TheMovie, Series/KamenRiderDenO (who's immune to changes in the timeline) demonstrates that the originals can do it too; [[spoiler:later on in the series, Zi-O's actions eliminate the retcon element, meaning that more Legend Riders actually get to help him battle their evil doppelgangers.]]

** ''Film/ManOfSteel'': No one knows about kryptonite yet, so the only one who's able to stop the rampaging Kryptonian General Zod is Superman, a Kryptonian himself, being strong enough to break Zod's neck.

** In general, the greatest weaknesses of and the only things that can destroy an Infinity Stone are other Infinity Stones and people empowered by an Infinity Stone. In ''Film/TheAvengers2012'', the fact that Loki's scepter can penetrate the Tesseract's shield hints at both their natures as respectively the Mind and Space Stone. Scarlet Witch highly effective against the same Mind Stone because she received her powers from it to the point that she can [[Film/AvengersInfinityWar destroy it]]. [[spoiler: Thanos uses all Six Stones to destroy themselves in ''Film/AvengersEndgame'', and later in the same film resorts to using the Power Stone to defeat the Space Stone-empowered Captain Marvel]].

A subtrope of MutualDisadvantage. An opposite of TacticalRockPaperScissors where each type of combatant has some other capable of [[CurbStompBattle curb stomping]] it. However, this can be a subtrope of ElementalRockPaperScissors if an element happens to be weak against itself. Compare BeatThemAtTheirOwnGame, HoistByHisOwnPetard, and SummonBiggerFish. Contrast LikeCannotCutLike.

* In ''Anime/NeonGenesisEvangelion'', the Evas [[spoiler:who are pretty much Angels anyway]] are usually the only things on Earth which can fight an Angel and win, because only they can break the Angel's AT fields. To be more accurate, Angels project AT fields so strong that only the similarly-sized Evangelions possess the power necessary to breach them. There are cases where the Evas weren't directly responsible for the victory. One was beaten by [[FeedItABomb blowing up a destroyer in its mouth]], Ramiel was taken down by a positron cannon fed with the entire country's power supply (wielded by an Eva, but the cannon did the work). Certain other options exist to hit the 180 million megawatt figure stated to be necessary to overcome Ramiel's AT-Field, which was one of the strongest of all the Angels (behind Tabris and Zeruel, most likely). The largest nuclear devices, for instance, could likely knock out an Angel, though nuking them isn't exactly an ideal solution.

* In ''Anime/HeroicAge'', all Nodos are so exceedingly powerful that the only thing that can fight a Nodos is another Nodos. Anything else is certain to get curb stomped. Even then, battles between Nodos can go on for quite a while. At one point, a Nodos battle lasts for ''300 hours straight''.

* ''Franchise/DragonBall''

* When the ComicBook/{{New 52}} version of ComicBook/{{Supergirl}} first fights the Worldkillers, one of them boasts that only a Worldkiller can defeat a Worldkiller. Supergirl exploits this by grabbing one Worldkiller's CombatTentacles and stabbing another one with them.

* In ''VideoGame/FireEmblemAwakening'' the last act of the game is spent finding a way to stop Grima, the ''BigBad'' of the game. Your party goes to a shrine to [[BigGood Naga]] in order to perform an awakening ceremony to hopefully give the [[SwordOfPlotAdvancement Falchion]] the power to slay Grima. However, Naga reveals after the ceremony that slaying Grima with the Falchion will only put him into a 1000 year sleep, and only his own power is strong enough to truly slay him.

** In general, the greatest weaknesses of and the only things that can destroy an Infinity Stone are other Infinity Stones and people empowered by an Infinity Stone. In ''Film/TheAvengers2012'', the fact that Loki's scepter can penetrate the Tesseract's shield hints at both their natures as respectively the Mind and Space Stone. Scarlet Witch highly effective against the same Mind Stone because she received her powers from it to the point that she can [[Film/AvengersInfinityWar destroy it]]. [[spoiler: Thanos uses all Six Stones to destroy themselves in ''Film/AvengersEndgame'']]

** The Dragon type is super effective against only one type -- itself. [[note]]Though Dragon-types are also weak against Ice-type and Fairy-type moves.[[/note]]

*** Hoopa Confined and Lunala are both dual-type Psychic/Ghost, so they have the dubious honor of having the only type combination with a [[QuadDamage double weakness]] to one of ''their own types''! [[labelnote:*]]Had a Pokémon with this type combination existed in the first generation, it would've truly had no weaknesses -- it was immune to Ghost, Bug-type moves did neutral damage, and Dark didn't exist. Not like those first two mattered, what with said moves being horribly underpowered.[[/labelnote]]

** When you start messing around with the ElementalRockPaperScissors, you may start getting combinations of types that wouldn't normally resist themselves paired with a type that is weak to said type -- like how the Fighting/Steel Lucario is weak to Fighting, the Bug/Grass Parasect is weak to Bug, and the Steel/Ground Steelix is weak against Ground. [[note]]These types are: Ground, Fighting, Flying, Rock, Fairy, and Bug. No, Normal doesn't count.[[/note]]

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* In ''Manga/JoJosBizarreAdventure'', a Stand zig-zags this with the ways it can be harmed. A Stand is [[PowersDoTheFighting a telekinetic construct of its user's spirit]], usually InvisibleToNormals, and can only be harmed by another Stand (which also inflicts [[{{Synchronization}} similar damage]] on its Stand User). However, a Stand User is just as vulnerable as normal people to being killed by conventional means, such as guns or swords; killing the Stand User will also destroy the Stand.