Takes One to Kill One: Difference between revisions

{{trope}}

 

 

This is oftentimes used as a [[Justified Trope|justification]] to why the protagonists, who oftentimes either are this kind of monster, can turn into one, or have one under their control, can seriously wail on the [[Monster of the Week]], and yet the [[Five Rounds Rapid|military forces and]] [[Police Are Useless|police are still useless]]. If the monster is unaffiliated with either side, it can lead to [[Always a Bigger Fish]]. If the protagonists are forced to become this type of monster to win, expect a [[My God, What Have I Done?]] moment afterwards.

 

A subtrope of [[Mutual Disadvantage]]. An opposite of [[Tactical Rock-Paper-Scissors]] where each type of combatant has some other capable of [[Curb Stomp Battle|curb stomping]] it.

 

{{examples}}

* In ''[[Neon Genesis Evangelion]]'', the Evas ({{spoiler|who are pretty much Angels anyway}}) are 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, the Evangelions are the most easily deployed and most reliable way to defeat an Angel. AT-Fields can be pierced by raw force, however. Ramiel, for instance, was defeated by charging up a positron cannon with enough juice to just blow a hole in him AND his AT-Field, all EVA-01 did was serve as a weapons platform as the cannon was unfinished and therefor had no deployment apparatus. 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.

* Ryo Takatsuki's [[Nanomachines|nanite-powered]] [[Super-Powered Evil Side]] in ''[[Project ARMS]]'' has a unique power to negate the [[Healing Factor]] of other ARMS.

* ''<nowiki>~Blood: The Last Vampire~</nowiki>'' has this as its basic premise.

* The plot of ''[[Eternal Sabbath]]'' revolves around getting Shura to kill Isaac, as Shura is the only one who understands Isaac enough to stop him.

* In ''[[Yu-Gi-Oh Ze Xal (Anime)|Yu-Gi-Oh! ZEXAL]]'', the [[Gotta Catch Em All|Numbers]] monsters cannot be destroyed in battle except against another Number. [[Subverted]] in that they can still be destroyed by card effects, and it's entirely possible to [[Power Nullifier|negate their invulnerability]] so that they can be destroyed by ''any'' monster.

* ''[[Puella Magi Madoka Magica]]'' seems to [[Playing With Tropes|play]] with this trope. At first, the Puella Magi magic appears to be the only way to kill Witches (straight trope), but it is eventually revealed that {{spoiler|Akemi Homura actually uses firearms and bombs}} (subversion) {{spoiler|to kill Witches off, because of her comparatively weak offensive powers}}. And then, in episode 11, {{spoiler|she blasts Walpurgis Night with literally thousands of explosions and doesn't even manage to scratch her (keep in mind she usually manages to kill witches off with barely one hundredth this firepower). For all intents and purposes, it turns out Walpurgis Night can only be defeated by a Puella Magi's powers}} (thus, double subversion).

** {{spoiler|And in a cruel double subversion, [[And Then John Was a Zombie|it turns out that Puella Magi are actually 'immature' witches.]]}}

== [[Live Action TV]] ==

* In ''[[Angel]]'' season 4, Angelus figures out that the only thing that can harm the Beast is a knife crafted from its own rocky hide. Which it had conveniently crafted already as an offering to its master.

{{quote| So you need one to kill one, but you got to kill one to make one. How does that work out? }}

** The only way to permanently kill Leviathans is for them to be eaten by other Leviathans. They can be killed via decapitation, but they only stay dead as long as the severed head is kept separate from the rest of the body. If the head is left close enough to the body, it will reattach and the Leviathan will come back to life.

** [[Sociopathic Hero|Alucard]] and [[Dhampyr|Blade]] are both vampires who hunt vampires.

** [[Van Helsing]]: The only thing that can kill Dracula is a werewolf.

 

 

* In ''[[Dungeons and Dragons]]'' 3rd edition and 3.5, creatures with damage resistance have their natural weapons (if existing) able to pierce that same resistance, so every creature is capable of killing its own species.

** In 4th Edition [[Dungeons and Dragons]], The Prince Of Hell Epic Destiny gets immunity to fire. He also gains the ability for his fire attacks to ignore resistances / immunity to fire, meaning only he can burn himself.

 

== [[Video Games]] ==

* In ''[[Breath of Fire]]: Dragon Quarter'', dragons can only be harmed by other dragons. This means that if Ryu transforms in a conventional battle (including the vast majority of boss battles), he is ''invincible''. There is one exception: A certain enemy dragon can be harmed with conventional weapons if a transformed Ryu attacks first and "breaks the defense".

** And the final boss must be [[Playing Tennis With the Boss|taken down with his own projectiles]].

* In ''[[Persona 3]]'' and ''[[Persona 4]]'', [[Summon Magic|Personas]] are actually {{spoiler|Shadows (with Shadows themselves being the coalesced feelings of despair and loathing in all people, so it can be said that Shadows are the Persona of humanity)}}. As such, they can (and have) {{spoiler|turn back on whomever they're a Shadow of and consume them}}.

* "???"-type enemies in ''[[Alter AILA Genesis]]'' are the enemies who use Psych-elemental attacks the most often, but they are also the only enemy weak to it.

** Many other enemies do this too; robots use Shock attacks the most, and humanoids tend to use Force, both of which are the elements they're most weak to.

* In ''[[Final Fantasy Tactics]]'', the "Faith" stat dictates not only a mage's attack power, but how much damage they incur from enemy spells as well. A character with very low Faith is thus virtually immune to magic, while a character with high Faith is very vulnerable.

* Dragons of [[The Elder Scrolls V Skyrim|Skyrim]] are otherworldy beings bound to flesh. Upon death, their souls do leave their bodies, but can easily return with help from another, making them functionally immortal. The only way to truly kill a dragon is for another dragon to [[Your Soul Is Mine|devour their soul]]. The player character, a mortal born with the soul of a dragon, is close enough to a real dragon to pull this trick off themselves.

 

== [[Western Animation]] ==

* [[Courage the Cowardly Dog]] had the Kangaroo Monster, a creature so [[Badass]] the only thing that could harm it...was ''another'' Kangaroo Monster!

* On ''[[South Park]]'' the only way to defeat a giant stone [[Abraham Lincoln]] is with a giant stone John Wilkes Booth.

** Also, immortal beings like Cthulhu can only be killed by other immortals.

** In another episode Dexter gives Dee Dee what he thinks is a silencing potion, but instead mutates her into a monster. The only way to get her to shut up? To become a giant monster himself and have a knock-down, drag-out kaiju battle!

* Parodied in a "What If" episode of ''[[Futurama]]'', where the Planet Express crew creates a Giant Zoidberg as only an "even equally big" monster could defeat a 500 foot tall monster rampaging through the city. [[It Got Worse|This fails miserably as Giant Zoidberg immediately goes on a power trip and rampages through the city, and so the two giants fight and kill each other in the ensuing turf war]].