History Main / MutualKill

* This is the EvilPlan behind ''The Internecine Project'' (1974), where the villain arranges to have four associates who [[YouKnowTooMuch know too much about him]] kill each other off (though not at the same time). [[spoiler:EveryoneDies by the end because one of the victims was suspicious and arranges for the villain to be sent a [[FingerLickingPoison poisoned message]] in the event of his death.]]

Compare DoubleKnockout, where both combatants inflict critical but non-lethal damage on each other. Similar to, though not quite, TakingYouWithMe, where one combatant orchestrates both of the killing blows. This is a common, albeit far from guaranteed, result of DeliberateInjuryGambit. When it happens during a MexicanStandoff, it's a BlastOut. If damage is fatal but does not prevent immediate retaliation, result may be the same (this includes TimeDelayedDeath and IncendiaryExponent). Could also be from a SelfDestructiveCharge or PoisonedWeapons. May involve a LastBreathBullet from one of the combatants.

* ''VideoGame/XenobladeChronicles'': Believed to have happened in the ancient battle between the Bionis and Mechonis, with Shulk even referring to their world being on the "Bionis' corpse". Over the course of the game, though, it becomes increasingly clear that neither of the two titans is truly dead, and they've merely been in a deep slumber.

* Near the end of ''Videogame/{{Yakuza}}'' 4, Katsuragi shoots [[spoiler: Yasuko]] in the back, resulting in a fatal wound. However, before her death, she manages to retaliate by popping a headshot right back at Katsuragi.

* This can easily happen using most hand weapons. Most weapons, when wielded, inherently create an opening when used to attack. For example, someone using a rapier in a lunge is vulnerable to a counter-attack. The lunging swordsman would defend against this by either by having an off-hand parrying implement or assuming their opponent wants to live and will defend rather than simply counter-attack into the lunge. Japanese swordsmanship is perhaps the only style of make a virtue of cutting your enemy down as he does you. Since sword-fighting occurred before modern medicine, there were all kinds of lethal but not instantly-incapacitating wounds like punctured lungs or punctured bowels. Then there's head trauma, which can cause sudden death hours after "''recovery''".
** In Fencing and HEMA, there are usually rules to deal with these situations.

*** The Liberty ship ''SS Stephen Hopkins'' and the German comerce raider ''Stier'', also sank each other.
** And logically its also possible for two aircraft carriers to sink each other, like when aircraft from IJN Hiryu fatally struck[[note]]It's possible the damage would have been repairable, but Yorktown was torpedoed by a submarine in its weakened state[[/note]] USS Yorktown followed by aircraft from USS Yorktown fatally damaging Hiryu.

** WWI AcePilot duo, Albert Ball (UK) and Lothar von Richthofen (Germany), who shot down each other 7 May 1917. However, while Richthofen was able to land his damaged plane without injury to himself, Ball crashed to his death.

* During UsefulNotes/TheAmericanCivilWar, the Confederate submarine ''H. L. Hunley'' attacked and sank the USS ''Housatonic'' with a [[RammingAlwaysWorks spar torpedo]]. Shortly after, the ''Hunley'' herself sank before making it back to Charleston, with the most popular theories for her sinking being an unsecured hatch (the ''Hunley'' rode very low in the water even while surfaced), damage from the ''Housatonic's'' crew firing on the ''Hunley'' during her attack, or possibly damage [[HoistByHisOwnPetard caused by her own torpedo.]] Finding a definite answer is difficult, as ''Hunley'' took her entire crew with her. The ''Hunley'' was raised in 2012 and found to be largely intact; the current theory is that the shockwave from the exploding torpedo (only twenty feet away from the hull) killed the crew and/or forced her into the soft seabed where the mud kept her stuck; even if any of the crew had still been alive, they would have been in no state to escape or free the stricken sub from the seabed.

* A well known photograph taken in [[https://www.snopes.com/fact-check/tale-gator/ 2005]] shows a snake that burst with an alligator coming out. The exact circumstances are unknown, but the snake [[DeathByGluttony may have burst trying to eat the alligator]], killing them both.
* The late comedian Norm Macdonald joked about how anyone who died of cancer (which would include himself) actually acheived this. After all, if the person dies, the cancer dies too. No one actually loses the battle with cancer, at worst it ends up deing a draw.

* In the first half of the ''Series/PowerRangersInSpace'' finale [[Recap/PowerRangersInSpaceS1E42CountdownToDestructionPart1 Countdown to Destruction]]", [[TheStarscream Darkonda]] makes his final bid to grab power by blasting Dark Specter with a planet-destroying missile. Unfortunately, Dark Specter then uses the last of his strength to devour Darkonda's ship just before he exploded, [[TakingYouWithMe taking Darkonda with him]].

* In the first have of the ''Series/PowerRangersInSpace'' finale [[Recap/PowerRangersInSpaceS1E42CountdownToDestructionPart1 Countdown to Destruction]]", [[TheStarscream Darkonda]] makes his final bid to grab power by blasting Dark Specter with a planet-destroying missile. Unfortunately, Dark Specter then uses the last of his strength to devour Darkonda's ship just before he exploded, [[TakingYouWithMe taking Darkonda with him]].

* In the first have of the ''Series/PowerRangersInSpace'' finale [[Recap/PowerRangersInSpaceS1E42CountdownToDestructionPart1 Countdown to Destruction]]", [[TheStarscream Darkonda]] makes his final bid to grab power by blasting Dark Specter with a planet-destroying missile. Unfortunately, Dark Specter then used his last own of strength to devour Darkonda's ship just before he exploded, [[TakingYouWithMe taking Darkonda with him]].

* In the first have of the ''Series/PowerRangersInSpace'' finale [[Recap/PowerRangersInSpaceE41CountdownToDestructionPart1 Countdown to Destruction]]", [[TheStarscream Darkonda]] makes his final bid to grab power by blasting Dark Specter with a planet-destroying missile. Unfortunately, Dark Specter then used his last own of strength to devour Darkonda's ship just before he exploded, [[TakingYouWithMe taking Darkonda with him]].

* In the first have of the ''Series/PowerRangersInSpace'' finale [[Recap/PowerRangersInSpaceE42CountdownToDestructionPart1 Countdown to Destruction]]", [[TheStarscream Darkonda]] makes his final bid to grab power by blasting Dark Specter with a planet-destroying missile. Unfortunately, Dark Specter then used his last own of strength to devour Darkonda's ship just before he exploded, [[TakingYouWithMe taking Darkonda with him]].

* ''Franchise/PowerRangers'': Darkonda and Dark Specter in ''[[Series/PowerRangersInSpace Countdown to Destruction]]''.
* One episode of ''Series/{{Psych}}'' features the death of the founder of a modelling agency. Shawn's first suspect is the victim's wife...until she dies during her husband's funeral. Then, during the climax, Shawn realized that they had killed each other: the husband had slowly been poisoning his wife (due to her being a bulimic) and [[TimeDelayedDeath ended up killing her postmortem]], and as Shawn figured, the wife had been behind the accident that had killed her husband at the beginning of the episode. Unfortunately, [[InspectorLestrade Lassiter]] is not amused that Shawn called him when there was no one alive to arrest.

* This is the theory of Mutually Assured Destruction. Second strike capacity is defensive in nature; it ensures that any kill will be a mutual kill and (hopefully) scares the enemy into not attacking. As such, a missile shield of some sort would, in the perverse logic of nuclear arms, actually allow an attack by preventing the kill from being mutual.

* In ''Anime/PuellaMagiMadokaMagica'', Kyouko sacrifices herself to MercyKill Sayaka after the later falls to TheCorruption. This also apparently happens to [[spoiler:Madoka]] in the [[GroundhogDayLoop previous timelines]], when she's the only magical girl left to fight [[TheDreaded Walpurgisnacht]]. The battle isn't shown, only the aftermath, with her either dead or [[spoiler:becoming a witch]] and the super-witch [[NoBodyLeftBehind seemingly destroyed]].

* In ''Anime/PuellaMagiMadokaMagica'', Kyouko sacrifices herself to MercyKill Sayaka after the later falls to TheCorruption. This also apparently happens to [[spoiler:Madoka]] in the [[GroundhogDayLoop previous timelines]], when she's the only magical girl left to fight [[TheDreaded Walpurgisnacht]]. The battle isn't shown, only the aftermath, with her either dead ([[spoiler:or becoming a witch]]) and the super-witch [[NoBodyLeftBehind seemingly destroyed]].

* In ''Anime/PuellaMagiMadokaMagica'', Kyouko sacrifices herself to MercyKill Sayaka after the later falls to TheCorruption. This also apparently happens to [[spoiler:Madoka]] in the [[GroundhogDayLoop first timeline]], when she's the only magical girl left to fight [[TheDreaded Walpurgisnacht]]. The battle isn't shown, only the aftermath, with her dead and the super-witch [[NoBodyLeftBehind seemingly destroyed]].

** This could be counted as subverted in that, in ''Film/TheRiseOfSkywalker'', he returns by transferring his soul into a clone body, but aside from George Lucas having fully intended this a permanent death for the Emperor, many fans are inclined to FanonDiscontinuity the sequel trilogy, mostly for reasons related to ''Film/TheLastJedi'', but also criticized that his return (which was [[UnexplainedRecovery not clearly explained in the film itself]]) renders Anakin's sacrifice (and the prophecy that he'd destroy the Sith) meaningless, and furthermore there is a plot hole regarding the destruction of the second Death Star.

* ''Literature/{{Gor}}'': Mentioned in a {{backstory}} anecdote from ''Priest-Kings of Gor''. Two men from different cities went on a {{quest}} and were to each other as brothers. After the quest was over they returned to their cities; the cities later went to war with each other and the two men killed each other on the field of battle.

** Spike and Vicious accost each other within lethal striking distance inside a cathedral in Episode 5 -- [[GunsVsSwords Spike with a Jericho pistol, and Vicious wielding a katana]]. Each strikes the other simultaneously in the shoulder. Using the arm of his other shoulder, Vicious grabs Spike's head and lifts him so that the latter's back faces a window mosaic three stories above the ground. Vicious then throws him through the window. As he breaks the window, Spike leaves a pinless grenade behind before he falls to the ground below. [[spoiler: [[ShrugOfGod Whether or not the results of these interactions kill the both of them is left to viewer discretion.]] discretion]]: [[AllJustADream the remaining episodes may be Spike's dream in an afterlife]], from a certain perspective.]]

** Spike and Vicious accost each other within lethal striking distance inside a cathedral in Episode 5 -- [[GunsVsSwords Spike with a Jericho pistol, and Vicious wielding a katana]]. Each strikes the other simultaneously in the shoulder. Using the arm of his other shoulder, Vicious grabs Spike's head and lifts him so that the latter's back faces a window mosaic three stories above the ground. Vicious then throws him through the window. As he breaks the window, Spike leaves a pinless grenade behind before he falls to the ground below. [[spoiler: [[ShrugOfGod Whether or not the results of these interactions kill the both of them is left to viewer discretion.]]]]

** Spike and Vicious accost each other within lethal striking distance inside a cathedral in Episode 5 -- [[GunsVsSwords Spike with a Jericho pistol, and Vicious wielding a katana]]. Each strikes the other simultaneously in the shoulder. Using the arm of his other shoulder, Vicious grabs Spike's head and lifts him so that the latter's back faces a window mosaic three stories above the ground. Vicious then throws him through the window. As he breaks the window, Spike leaves a pinless grenade behind before he falls to the ground below. [[spoiler: [[ShrugOfGod Whether or not the results of these interactions kill the both of them is left to viewer discretion]]: [[AllJustADream the remaining episodes may be Spike's dream in an afterlife]], from a certain perspective.]]

* [[Anime/DigimonAdventure]]: [=MetalEtemon=] directs a lethal energy blast at Mimi, but [=SaberLeomon=] takes the hit and is mortally wounded. However, he survives long enough to impale [=MetalEtemon=] with his claw (as a result of Zudomon denting him with his hammer in between the two events), finishing him off for good.