->''"Could you kill your best friend?"''
-->-- ''Film/BattleRoyale''

%% One quote. Extras go on the quotes tab.

Sometimes, a character you care for is going to die. Rather than killed off by the bad guys or some cosmic whim, though, the murderer is [[TrueCompanions another character who cares very much for the deceased]]. Perhaps your little sis has become a TragicMonster and needs to be [[StakingTheLovedOne staked]], or maybe you have to [[FightingYourFriend Fight Your Friend]] to the death. Occasionally it's a case of ShootTheDog or MercyKill. In any case, the characters know each other, as well as their relationship to each other. And the killer knows that the other has to die for anything to be resolved. In some cases leads to CradlingYourKill.

In video games, this is invariably a PlayerPunch. This trope usually doesn't villainize the killer, since the now-dead character generally has to be killed to right wrongs, or at least keep the story going. Doesn't stop him or her from [[HeroicBSOD feeling like crap]] afterwards, though.

May or may not overlap with SelfMadeOrphan or SiblingMurder.

!!'''As a DeathTrope, several if not ALL Spoilers will be unmarked ahead. Beware.'''


[[folder:Anime and Manga]]
* ''Anime/NeonGenesisEvangelion'':
** Shinji killing his only friend Kaworu, in order to save humanity. Kaworu actually ''[[GoOutWithASmile smiles]]'' when he tells Shinji he has to die...
** ''[[GainaxEnding The End of Evangelion]]'' takes this UpToEleven. Though saying that may be {{Cliche}}, there are examples to support the claim:
*** During a mindprobe sequence, Shinji's heart is attacked by several of his close friends [[spoiler: - Asuka doing most of the work]]; as soon as his plea for mercy is rejected, he strangles [[spoiler: Asuka]].
*** After this action, Shinji - having the power of God - decides to kill [[spoiler: everyone about whom he's ever cared]].
*** Rei [[spoiler: carries out his wishes]].
*** After this decision, every important-to-semi-important character is visited by a vision of the character they love the most [[spoiler: only to break their Ego Barrier/AT-Field and literally destroy them]].
*** A noteworthy, possibly surprising example of this act is Hyuga's initial horror at the apparition in front of him [[spoiler: before the apparition morphs into Misato and plants a [[KissOfDeath wet smooch and loving caress onto him, thereby completely disassembling him physically]].]]
* ''Anime/BaldrForceEXEResolution'': Tohru has to kill Ren to keep her from destroying everything in the Wired.
* Raziel from ''Manga/AngelSanctuary'' forces himself to shoot his beloved superior Zaphikel when the latter transforms into a ghoul.
* ''Anime/BloodPlus'': Due to PsychoSerum Delta 67, the heroine Saya's adoptive father George Miyagusuku starts to turn into a mindless bloodthirsty monster and she must reluctantly kill him before the drug takes effect.
* ''Anime/CodeGeass'':
** Lelouch (as Zero) is forced to shoot Euphemia after he accidentally Geasses her into killing all the Japanese, sending her on a rampage. Just as he does it, he mentally bids her farewell, and even thinks to himself that she was [[BrotherSisterIncest his first love]]. He's later shown angsting over it.
** Then there's the finale, where Suzaku, disguised as Zero, stabs Lelouch in a ThanatosGambit. He's shown crying while doing it. It's also especially tragic because everybody except Lelouch thinks Suzaku is dead and since he was an accomplice in the ZeroApprovalGambit, he can't go public or he'll ruin Lelouch's plans. Also, he can't take the easy way out because his "live" Geass forces him to do exactly that.
* ''Anime/WeissKreuz'' loves this trope. ''Loves'' it. Aya has to kill two of his mentors; Ken has to kill his best friend, girlfriend, surrogate mother, ''and'' old friend's brother; and Youji gets to kill ''three'' girlfriends.
* ''Manga/{{Naruto}}'':
** Sakura has decided to kill Sasuke with her own hands, to save their land and spare him from falling even lower than he already has. Subverted, as when push comes to shove, she can't bring herself to do it and is nearly killed herself.
** In the backstory, Itachi did this when he slaughtered the Uchiha Clan, including his own parents whom he killed last, to pre-empt a coup. A flashback shows him about to cut down his parents who aren't even trying to fight back. Just to twist the knife further, they spend their final moments assuring Itachi that they still love him and respect his decision and ask him to look after Sasuke. Itachi is crying the entire time. Speaking of the Uchihas, the Mangekyo Sharingan is unlocked by the death of a loved one ([[spoiler: Kakashi's]] turned out to be a SuicideByCop, so it doesn't need to be deliberate).
** Kakashi discovers that [[spoiler:his hero and childhood friend Obito Uchiha]] caused the Fourth Shinobi War, which makes killing him Kakashi's responsibility and no-one else's. An interesting example, since Naruto (the idealist) still wants to redeem him, while Kakashi [[spoiler:and Minato Namikaze]], who knew and loved him, fight only to kill. Subverted when [[spoiler: after Obito is defeated, just as Kakashi is about to kill him, Minato stops him from doing so so that Obito can have a chance at redemption.]]
* In ''Manga/RGVeda'', believing that Sōma can't survive the battle and will be killed, Kendappa-ō kills her herself, and then commits suicide because she sees no point in living on without her.
* ''Manga/{{Bleach}}'': Rukia Kuchiki was forced to kill her mentor and first love, Kaien Shiba, when he became possessed by a Hollow.
* In the ''Manga/{{Claymore}}'' universe, this sort of thing happens all the time due to the whole ICannotSelfTerminate thing. The first instance occured in the very first volume when Clare was called upon to MercyKill her girlhood friend Elena.
** The instance with Raphaela is particulary memorable, tough.
* ''Anime/GaReiZero'': Yomi [[MemeticMutation ;_;]] It's even the anime's tag line!
** ''Manga/GaRei'': Yomi [[MemeticMutation ;_;]] (''twice'', [[TraumaCongaLine at that]]).
* In ''LightNovel/{{Corsair}}'', this is a major issue for Canale. His murder of Sesaam, his lover at the time, is the biggest instance but he also feels responsible for his mother's suicide and the general death and destruction that follow him wherever he goes.
* In ''Manga/ProjectARMS'', all of the heroes say, in no uncertain terms, that they won't hesitate to kill Ryo if he's taken over by the Jabberwock. Given that he fears that happening to him, it's actually ''comforting''. At the end of the manga, he remembers this when he has to bring himself to kill Katsumi, who is possessed by Alice. Fortunately, she gets better.
* ''Anime/PuellaMagiMadokaMagica'':
** [[CoolBigSis Mami]] during the third timeline of episode ten's GroundhogDayLoop hits the DespairEventHorizon upon learning the true nature of Magical Girls after [[TragicMonster Sayaka]] turns into a witch and has to be killed. Not wanting the rest of the magical girls to turn like her, Mami kills Kyouko, but before she is able to kill Homura and Madoka before presumably ending her own life, Madoka shoots her. After doing that, poor Madoka collapses in tears, asking the newly released Homura between sobs why did such things have to happen.
** An even more tragic example is later in the third timeline. Madoka and Homura manage to destroy Walpurgisnacht, but both are injured, exhausted and in danger of becoming witches. Madoka uses her last Grief Seed to remove the darkness from Homura's Soul Gem in order to spare her from becoming a witch, and Homura returns the favor by tearfully {{Mercy Kill}}ing Madoka before she becomes a witch.
** Madoka manages to do this ''accidentally'' when she throws Sayaka's gem off a bridge to stop her from fighting Kyouko, not realizing that [[SoulJar it literally contains her soul]]; though fortunately she was OnlyMostlyDead. Sayaka is KilledOffForReal via this trope after she becomes a witch: Kyouko destroys her by smashing her own soul gem so they can be TogetherInDeath.
* Realising that he has to do this to his LoveInterest, [[EmotionlessGirl Yin]] because her SuperPoweredEvilSide will destroy the world if he doesn't causes Hei from ''Anime/DarkerThanBlack'' to [[HeroicBSOD BSOD]] big time leading to him becoming the drunken JerkAss we know from the second season.
* This is the entire point of the Sacrifice required to become a demon from ''{{Manga/Berserk}}'', as first revealed in the Guardians of Desire arc. By consigning that which you most love to be eaten by demons, the would-be Apostle (or Godhand) cuts himself or herself off from humanity and opens himself or herself to evil. Unlike most of the examples on this page, this act is presented as a monstrous betrayal of everything the person holds dear and a crossing of the MoralEventHorizon, both because of the {{Cruel And Unusual Death}}s often suffered by those who get the Brand put on them and due to the added little detail that anyone sacrificed in the creation of a demon gets his or her soul condemned to Hell for all eternity.
* ''Taimanin Asagi'' has Asagi doing this to Kyousuke close to the end. He had been turned into a monster, he was lucid at that moment, and she said "I love you" just before breaking his neck and killing him quickly. You would have to have a heart made out of stone not to feel anything over that.
* In ''Manga/MaiHime'', Natsuki takes it upon herself to end her best (and for a long time, only) friend Shizuru's rampage, knowing that both of them will die in the process.
* ''LightNovel/KyoKaraMaoh'' likes to flirt with this trope. Particularly Conrad and Yozak--they've been best friends for decades, are probably more comfortable with one another than with anyone else in the world, are the only survivors of their HalfHumanHybrid battalion. But in the second episode in which they appear together, Conrad threatens to kill Yozak if he messes with Yuuri again. This scene is ''so much freakier'' when you see it again after learning all the background between the characters.
** Conrad also throws Yozak off a cliff [[spoiler: during his FaceHeelTurn, right after Yozak attacked him while giving a declaration that was basically, 'you're my best friend and my captain and if this is how it's going to be I'll kill you myself.']]
** And in the weird guest episode with the mountain of betrayal miasma, where everyone except [[IncorruptiblePurePureness Yuuri]] became convinced that everyone else had been compromised by the mist of betrayal and become their enemy. Yozak and Conrad had rather a good duel in the snow.
*** Even more impressive in that episode was when [[{{Tsundere}} Wolfram]] became convinced that Yuuri had gone crazy was going to kill him and ''didn't'' invoke this trope, just curled up and waited. PowerOfLove.
** When Conrad and Yuuri met in the coliseum it looked like this was going to happen, too, and about ten episodes later it [[spoiler: very nearly did.]]
* In ''Manga/{{Amakusa 1637}}'', two events shattered [[spoiler: Naozumi Yatsuka]]'s view of the world. One was the phenomenon that got him and his friends TrappedInThePast. The other was killing the first person in said past who understood him, his young and handsome slave Shirou. [[spoiler: [[http://en.wikipedia.org/wiki/Amakusa_Shir%C5%8D Yes, that Shirou]].]]
* Riddle from ''Manga/UndertakerRiddle'' killed his best friend and former king of the Catacombs, Sigurd, after he went DrunkWithPower and almost destroyed the Catacombs.
* In ''Anime/TekkamanBlade,'' all of the enemy Tekkamen are either D-Boy's family or close friends, including two brothers (one of them his twin) and a sister-in-law.
* ''Manga/SchoolLive:''
** Kurumi had a crush on a boy who became a zombie. She "killed" him in self defense.
** Kurumi tries to do this [[spoiler:their zombified teacher, Megu-nee,]] however cannot bare to. [[spoiler:Megu-nee bites her and later Miki, who is the only one who didn't know Megu-nee, 'kills' her]].
** Yuuri gets dangerously close to this when she almost {{mercy kill}}s [[spoiler:Kurumi]], who is becoming a zombie. Thankfully Miki appears with an antidote before she can. It still might occur in the future though.
* In the ''VideoGame/{{Strider}}'' manga, Hiryu was forced to do this to his sister Mariya after she went insane and started murdering other Striders. He tried to talk her out of fighting, but being unable to, was finally forced to fight back and [[ImpaledWithExtremePrejudice pierce her through with his Cypher]]. This would weight heavily on his mind afterwards, eventually leading to him leaving the Striders.
* In ''Anime/OccultAcademy'' Maya is forced to behead her fathers possessed corpse. He was technically already dead but the results are similar.
* After having died several episodes prior, Kanou from ''Manga/NurseAngelRirikaSOS'' is revived by Buros with an evil show. This causes Ririka to have to kill him after learning he is affiliated with Dark Joker.

[[folder:Comic Books]]
* In ''ComicBook/ForTheManWhoHasEverything'', Franchise/{{Superman}} has to do this to escape the Black Mercy. In accepting that his wonderful new life is a dream, he causes the dream Krypton to explode just like the real one. Similarly, Franchise/{{Batman}} has to let Joe Chill kill Thomas and Martha Wayne in his dream just as Chill did in life to escape the Mercy.
* ComicBook/{{Psylocke}} had to do this in ''[[ComicBook/XForce Uncanny X-Force]]''. Twice. The first was her lover, Archangel; he was possessed by Apocalypse, forcing her to completely erase his mind. The second was her brother, Jamie; his future self was a multiverse-conquering demon, so she killed him to save the worlds.

* The ending to ''Film/MillionDollarBaby''. The film's star boxer has suffered a career-ending injury, is paralyzed below the neck, has no hope of recovery beyond being immobile for the rest of her life, and because she is no longer able to pursue her dream of being a boxer, she wants to die, but cannot kill herself due to her injuries. Her manager, who has during the course of the movie become like a father to her, later makes the painful decision to cut off her life support and give her a massive dose of tranquilizers to avert her prolonged suffering.
* Averted in ''Film/{{Serenity}}'': "bullet in the brainpan squish." Just enough to scare the audience into thinking that was the planned ending. It is easy to imagine [[Creator/JossWhedon the writer]] pulling that one.
* In John Woo's ''Film/TheKiller'', the title character has to put a bullet to Sidney Fung, his best friend, in an ICannotSelfTerminate moment, after he went through serious hell to get the money the Killer needs to have Jenny's eyes fixed to him and got shot by the bad guys.
* Subverted in the ending of ''Film/PansLabyrinth'', when Ofelia has to kill her baby brother to prove herself as a princess of another world. She refuses to do so. Soon, she's killed... and then she's spirited away to her real home anyway.
* DoubleSubverted in ''Film/KillBill''. At first, all we see of The Bride is her RoaringRampageOfRevenge against Bill, her ex-lover, but after she kills him, she breaks down sobbing for several moments.
* ''Film/ShaunOfTheDead'': Shaun shoots the [[NotUsingTheZWord zombie]] Barbara after her transformation.
* ''Film/TheUsualSuspects'' has a sickening version. According to a legend, when Keyser Söze was a small-time gangster, someone once tried to take him down by going after his wife and children. He came home to find them being held hostage, guns and knives being held to them, pleading eyes, etc. Not to be cowed, he ''killed them all himself'', then the shocked hostage-takers, [[RoaringRampageOfRevenge "then their parents, then their parents' friends..."]]
* ''Film/XMenTheLastStand'':
** Jean Grey as the Phoenix kills both Professor X and Scott Summers.
** Wolverine is forced to kill Jean to stop her murderous Phoenix alter-ego from destroying everything.
* As mentioned in the Literature section, ''Film/OldYeller'' is one of the oldest examples in film. At first there is a HopeSpot tease when Travis pens the dog in a corncrib, hoping he won't turn rabid -- he does.
* Will Smith's dog in ''Film/IAmLegend''.
* Both the film and book version of ''Literature/OfMiceAndMen'' show two examples. The first is a subversion depicting a man who has to have someone shoot his rabies-infected dog. He laments that he didn't do it himself. It is later invoked when [[ItWasHisSled George has to kill Lenny]] to save him from an angry mob.
* In ''Film/TinkerTailorSoldierSpy'', Jim Prideaux and Bill Haydon are known as "The Inseparables", their relationship so close that it's possibly [[HoYay not totally platonic]]. But when it turns out Haydon is TheMole, Prideaux is the one who executes him.
* ''Film/{{Ransom}}''. Corrupt cop Jimmy Shaker seems to care for Maris, his girlfriend and fellow kidnapper. When he kills the two expendable remaining kidnappers to make himself out as a hero cop, she shoots him in turn, clearly expecting him to dispose of her as well. He seems a bit shocked at this before he kills her as well with apparent remorse.
* In ''Film/TheWolfman2010'', the first werewolf kills his wife and son; Lawrence kills [[spoiler:his father]] and almost kills Gwen too.
* First invoked, then cleverly subverted in ''Film/{{Zombieland}}''. Wichita asks Tallahassee and Columbus to perform a MercyKill on her infected sister, Little Rock, then stops them and insists that she be the one to do the deed. [[spoiler:[[SubvertedTrope She then promptly turns the gun on the two men so that she and her NOT-infected sister can steal their weapons and vehicle]]]].
* In ''Film/{{Pixels}}'', the confrontation between Ludlow and Lady Lisa has shades of this, with Ludlow unable to bring himself to kill the love of his entire life.
* ''Film/IShotJesseJames'': Robert Ford, one of the closest friends of UsefulNotes/JesseJames, is the one that kills Jesse himself. The ''love'' part of the trope becomes clear at the end of the film during [[spoiler: Bob's DyingDeclarationOfLove towards Jesse]].
* ''Film/MonsieurVerdoux'': Implied. There is something in the way Charlie Chaplin (as the titular anti-hero) delivers his vague statement about losing his wife and child to a "happier place" (ie. Heaven), after losing everything in a stock market crash, that hints that he may have, shall we say, given them a "helping hand".


* The end of ''Literature/OldYeller'', where Travis has to ShootTheDog after Old Yeller has defended the family from a rabid wolf. Unlike the film, Travis knows the dog will inevitably succumb to rabies and shoots him as soon as he sees the dog's injuries.
* Averted in the story of the Sacrifice of Isaac in Literature/TheBible. It turned out to have been a SecretTestOfCharacter for Abraham.
* In ''Literature/{{Outlander}}'', Jamie has to kill his godfather, Murtagh, after he's grievously wounded at the battle of Culloden.
* In the Creator/StephenKing novel ''Literature/SalemsLot'', Ben is forced to kill Susan after she becomes a vampire.
* In the finale of the novel ''Literature/OfMiceAndMen'', George has to kill his best friend Lennie to save him from being lynched after the latter [[AndCallHimGeorge kills Curley's wife by breaking her neck by accident]].
* Creator/RosemarySutcliff's ''Literature/TheMarkOfTheHorseLord'' begins with the gladiator hero having to kill his best friend in the arena.
* In ''Literature/TheSagaOfLartenCrepsley'', near the end of the series, the protagonist killed his vampire brother, Wester. Although it is obvious Larten still cared deeply for his brother, Wester had betrayed Larten by killing his human wife and blaming the vampaneze. Wester hoped that he could use Larten, who had considerably more authority in the vampire society, to start a war between the vampires and the vampaneze.
* In Creator/AgathaChristie's ''[[Literature/MissMarple Nemesis]]'', a young woman who is about to elope is murdered by her guardian because she was loved by her too much.
** Also occurs in ''Literature/AMurderIsAnnounced''. One of the victims was killed by someone who loved them, out of fear that she was inadvertently revealing too much about the first murder.
* At the climax of ''[[Literature/TheDresdenFiles Changes]]'' Harry has to kill Susan once she fully turns into a Red Court vampire, turning their bloodline curse back against the Red Court and wiping them out.
** After he [[DealWithTheDevil becomes the]] [[JumpingOffTheSlipperySlope Winter Knight]], Harry himself is killed by Molly Carpenter[[note]]using Kincaid as a proxy[[/note]], a girl who has loved him for years. Everyone [[spoiler:except Charity]] mistakes Molly's guilt for mourning.
* The tragic climax in "Mastiff", the last book in the Literature/ProvostsDog trilogy. [[spoiler: The main character's father figure, Tunstall, betrays her and the crown, bribed by a noble title he can use to marry the lady knight he loves. Beka is duty-bound to capture him and bring him to justice for his crimes, while Tunstall, on his part, knows he'll only escape if he kills her. In the end, Beka just barely defeats him, he dies of blood-loss and exposure, and his spirit is terribly regretful for what he did.]]
* In ''Literature/AncillaryJustice'', [[spoiler:the AI of the ship Justice of Toren is made by [[TheEmperor the Lord of the Radch]] to kill Lieutenant Awn, one of her favorite officers. Immediately afterward Justice of Toren rebels, embarking on a quest for revenge that drives the rest of the book.]]
* In Literature/{{Beloved}} by Toni Morrison, Sethe [[spoiler: kills her daughter to prevent her from spending her life in slavery.]]
* In the ''Literature/SpiralArm'' series, Gidula views affection as a weakness, and personally kills anyone he begins to feel affection for in order to free himself from that weakness. He killed his wife, infant child, and number one minion for this reason, and attempts to kill Ravn Olafsdottr as well.
* StarWarsExpandedUniverse - This seems to be a rite of passage for Sith. Jedi avoid any deep attachments, part to avoid this trope. Sith are encouraged to embrace their passions, but LoveIsAWeakness as it leads to mercy, and there can be no weaknesses for an enemy to exploit or impediments to one's destiny. One of the more tragic cases was where [[VideoGame/StarWarsTheOldRepublic Darth Malgus]] became fond enough of his Twi'lek SexSlave to make her his common-law wife. The two of them [[BattleCouple fought side by side]] at the sacking of the Jedi temple, but she was injured in the fighting while protecting him. Another Sith mocked Malgus for his affection, stating that she was a weakness that could be used against him. Malgus ''agreed'' and murdered his "wife" in her sickbed. Of course, since he was a high-ranking Sith, and she was just a Twi'lek SexSlave, no one in the Empire cared.

[[folder:Live Action TV]]
* In the re-imagined ''Series/{{Battlestar Galactica|2003}}'', Colonel Tigh has to poison his wife after she betrays the resistance on New Caprica (which she did to save his life).
* ''Series/GameOfThrones'':
** Meera puts her brother, Jojen, out of his misery in "The Children."
** Shae is strangled to death by Tyrion in self-defense, even though Tyrion admits to his father that he still loved her.
* ''Series/{{NCIS}}'' - Ziva kills her brother Ari and is never able to mention him again without visibly stiffening or crying.
* In ''Series/{{House}}'', Wilson does this when he turns off Amber's life support. For everybody else, though, it was AlasPoorScrappy.
* In ''Series/{{Torchwood}}: Children of Earth'', Jack has to sacrifice his grandson.
* Creator/RussellTDavies seems to like this trope. In ''Series/TheSecondComing'', Steven Baxter, who also happens to be the son of God, is poisoned by his girlfriend [[MeaningfulName Judith]]. She does tell him that the food is poisoned, but he finds that she is right, he [[TearJerker must die]].
* Steven Moffat's not letting off with this trope either, playing it heartbreakingly straight with Rory in ''Series/DoctorWho'', who accidentally shoots Amy in an attempt to hold off Auton control of his mind.
* In ''Series/{{Merlin}}'', Merlin poisons Morgana -- who was unaware that she was the vessel of the Knights of Medhir -- because [[IDidWhatIHadToDo he did what he had to do]] in order to save Camelot, but at the price of killing his friend and someone he cared about. Many fans, while praising the acting of Colin and Katie, did not agree with Merlin's actions. Also a ShootTheDog moment.
* In ''Series/{{Nikita}}'', Alex shoots Thom, whom she had feelings for and even kisses him before he dies.
* Examples abound in ''Series/{{Supernatural}}'', both with the main cast and side characters.
** Bobby kills his wife when she's possessed by a demon. Then he kills her again when [[TheGrimReaper Death]] brings her back to life but learns that she's turning into a flesh-eating zombie. Naturally it pains him a great deal.
-->'''Bobby:''' She was the love of my life. How many times do I have to kill her?
** This is the background of recurring antagonist BloodKnight Gordon Walker, whose sister was turned into a vampire.
** In the season one finale John Winchester ordered Sam to shoot him with the Colt to take the demon out as well. (He didn't.) And a few episodes later John's final direction to Dean was that he 'had to save Sam,' or he 'might have to kill him.'
** Sam's mid-Season Two insistence that Dean promise to do just that if Sam goes darkside. Dean promised. He was lying.
** Sam's first girlfriend after his [[DeathByOriginStory episode-one bereavement]] turns out to be a werewolf who ''asks'' him to kill her. Or there's that time Sam nearly strangled Dean to death, or that time Sam shot Dean, or that time Sam was possessed and shot Dean, and possessed and killed him in the BadFuture.
** Downplayed in Season Six, with soulless [[FanNickname Robo-Sam]] determined to prevent Dean from restoring his soul. Rogue angel Balthazar informs him that to get his soul to reject reunion with his body he needs to pollute it with a crime such as patricide. Robo-Sam can't feel love, but apparently Sam's regard for Bobby as a surrogate father is enough for murdering him to be 'good enough.'
** The ArchangelMichael spends Season Five attempting to kill his beloved brother [[{{Satan}} Lucifer]] in accordance with God's will.
** "Hammer of the Gods" has a fight to the death between Lucifer and his [[EvenEvilHasLovedOnes other beloved brother]] Gabriel. Lucifer wins.
** Once you've got Dean messing around with an ArtifactOfDoom called the ''Mark of Cain'', of course the characters have every reason to fear that Sam may have to kill Dean to prevent the evil-inducing effects of the Mark, or that this induced evil itself might make Dean kill Sam.
** Turns out that if Dean dies with the Mark he simply comes back as a demon who is only too happy to give into the Mark's influence. Even Death himself can't kill Dean permanently, but does offer to transport him to a PrisonDimension where he can't hurt anyone else. The only condition is that Dean has to kill Sam, because Death knows that as long as Sam is still alive he will tirelessly search for a way to bring Dean back. [[spoiler:Dean ends up [[DidYouJustPunchOutCthulhu killing Death instead]]]].
** Plenty of lesser instances, particularly where family members or {{Love Interest}}s of both recurring and incidental cast turn out to be or turn into monsters.
* Series/{{Buffy|the Vampire Slayer}} to Angel in the season two finale is the obvious one (although he recovered).
** And, as evidenced in flashbacks on ''Series/{{Angel}}'', Holtz had to kill his daughter after Angelus (or possibly Darla) turned her into a vampire.
** Also in ''Angel'', Gunn stakes his sister after she is turned into a vampire.
* In ''Series/{{Charmed}}'', Phoebe needs to overcome her emotions and vanquish her husband and HeelFaceRevolvingDoor Cole. Three times.
* Played with in ''Series/RobinHood''. In the finale of season two Guy of Gisborne stabs Marian to death after she reveals her love for Robin Hood. The crime of passion ends with him being guilt-ridden for the rest of the show's duration, and even in his dying moments he doesn't hold out any hope that he'll ever see her again in the afterlife. He also gives his little sister a vial of poison so that she can kill herself, even after she tells him: "you loved me once."
* This is the philosophy of BigBad John Wakefield on ''Series/HarpersIsland''. He also tries to make Henry, his son and accomplice in the murders, kill the woman he loves. Henry refuses.
* In the 4th season finale of ''Series/TheMentalist'', Lorelei suggests that in order to become his disciple, Jane bring Red John a gift- the dead body of Teresa Lisbon, his close friend and partner. Subverted in that he only pretends to kill her.
* In ''Series/OnceUponATime'' Regina has done this ''three times''. The first time was when she killed her father (who is also one of the only people who love her) to get her revenge. The second was when her one true love was brought BackFromTheDead (by someone else) and CameBackWrong, necessitating a MercyKill. She really didn't take that well. Finally, Snow White tricks her into unintentionally killing her mother, who is pretty much the last person left that she does love. The end result has left her very [[BrokenBird broken]], very bitter, and very dangerous.
* It's kind of a theme on ''Series/{{Farscape}}'', how many times the crew members kill or almost kill each other.
** Part of Zhaan's backstory is that she killed her lover because he tried to seize power on their homeworld with the help of the Peacekeepers. Subverted with D'Argo who was wrongfully imprisoned for killing his wife (she was actually killed by her own brother.)
** Indirect example: Aeryn betrayed her lover to the Peacekeepers; he was arrested for treason. They undoubtedly tortured and killed him, which would not have happened if Aeryn hadn't turned him in.
** As a Website/TelevisionWithoutPity recapper put it: "Every time John's confronted with an Aeryn that's not what she seems, that doesn't love him, and his heart breaks, and he kills her, take a shot."
* In the ''Series/MastersOfHorror'' episode "Imprint", Christopher believes the prostitute Komomo to be the love his life. He ends up accidentally murdering her during his hallucinations.
* In ''Series/StarTrekTheNextGeneration'', Worf is paralyzed from the waist down and asks Commander Riker, as his friend, to do this for him in a sort of Klingon ritual [[MercyKill assisted suicide]]. Riker refuses on the grounds that under the ritual, it's properly the duty of the eldest son. Unwilling to ask this of Alexander, Worf opts for a dangerous experimental surgery instead.
* ''Series/ThatMitchellAndWebbLook:'' Played for very dark laughs in one sketch, where a man strangles his pregnant wife after she declares that not only does she not mind the [[FauxHorrific avocado-coloured bathroom]], she actually likes it.
* On ''Series/{{The 100}}'', Clarke has to kill Finn, the boy she had fallen for, [[MercyKill so at least his death will be quick, compared to what the Grounders have planned for him.]]

* Music/TheDecemberists' Culling of the Fold is, basically, about this. For pretty much no reason. Just because someone's got to do the culling of the fold.
* Played with in [[https://g.co/kgs/1XrK9x Ga1ahad and Scientific Witchery]] by Mili, which is about a knight on a mission to kill the witch who created/reanimated him, and whom he had a past romantic relationship with. [[spoiler:They seem to reconcile in the end, though...]]

* [[Myth/GreekMythology Agamemnon]] had to kill his [[OffingTheOffspring daughter]] Iphigenia so that the Greek fleet could sail...(opinions differ as to whether he actually did the deed.)

* In ''Theatre/TwelfthNight'', Orsino all but ''names'' this trope in the final scene, when he believes [[SweetPollyOliver "Cesario"]] to have betrayed him:
-->'''Orsino''': Why should I not, had I the heart to do it, Like to the Egyptian thief at point of death, [[TropeNamer Kill what I love?]]
* ''Theatre/{{Othello}}'' is led by the lies of ManipulativeBastard Iago to do this to his wife Desdemona.
* In Music/RichardWagner's "Ring", Wotan does this to his son Siegmund in ''Die Walküre'' and Brünhild to Siegfried in ''Götterdämmerung'', although the actual killing is done by Hunding in the first case, and by Hagen in the second.
* Judas in the musical ''Theatre/JesusChristSuperstar'' (the Biblical text itself could be basis for this trope too, depending on how you look at it).
-->I don't believe he knows I acted for our good
-->I'd save him all the suffering if I could

[[folder:Visual Novels]]
* Frequently occurs in ''VisualNovel/HigurashiWhenTheyCry'' as the main characters are TrueCompanions yet often kill each other in different arcs. Keiichi in ''Onikakushi-hen'' might be the truest to this trope. He killed [[spoiler:Mion]] and [[spoiler:Rena]] in self defense, crying while doing so. The series implies he's in love with one of them, though which one depends on the arc (''Onikakushi'' itself suggests [[spoiler:Keiichi loved Rena]]). In an even more depressing twist, [[spoiler:in reality they were of no harm and he was simply [[ThroughTheEyesOfMadness insane and thought]] they were trying to kill him.]]

[[folder:Video Games]]
* Helena in ''VideoGame/ResidentEvil6'', when she's forced to kill her younger sister Deborah who's been infected by the C-virus.
* Minerva from ''VideoGame/FireEmblemShadowDragon'' wants to be the one to kill her brother Michalis, an enemy of the protagonist's group:
-->'''Minerva''': (...) Even now, some part of me loves him.
-->'''Minerva''': ...I love him enough to spare him death on some stranger's sword, do you see? Let him be punished by my hands.
** Can be done in ''VideoGame/FireEmblemAwakening.'' [[spoiler: Lucina goes to kill the Avatar when she realizes that the Avatar will soon kill Chrom (her father). If the Avatar is Lucina's Mother or Husband, the scene gets [[TearJerker very emotional.]]]]
* This may happen in ''VideoGame/MassEffect3'' if you played a male Shepard who romanced Jack in the second game and then didn't do the Grissom Academy sidequest - when you get to the Cerberus base in the endgame, you'll find audio logs of Jack being tortured and then have to fight and kill her after she's been forcibly transformed into a Phantom.
* ''VideoGame/MetalGearSolid3''. The player, as Naked Snake, is actually forced to press the button and shoot The Boss while she's down.
** The end cutscene twists the knife by revealing that The Boss was a FakeDefector after all, and it was her sworn duty to be killed by Snake in order to prevent a nuclear war.
** The Boss had to experience something similar: She ended up having to go to Tselinoyarsk in 1962 to fight The Sorrow, and the flashbacks shown when Snake regains consciousness implies that she was unwilling to kill The Sorrow. Peace Walker explains the exact circumstances of what happened: The Philosophers forced them to fight each other to the death under the threat of Ocelot's life if both survive.
* ''Franchise/ShinMegamiTensei'', particuilarly mainline games, likes to do this, [[AlignmentBasedEndings as as consequence of pursuing one alignment and rejecting the others]]:
** ''Franchise/ShinMegamiTenseiI'': Side with Law? Your Law-aligned friend is killed at the hands of your Chaos-aligned friend, and then you have to kill your Chaos friend. Side with Chaos? After your Chaos friend is killed by an artifact that he couldn't handle, you then have to fight your Law friend. On Neutral? You kill ''both'', because they firmly believe that the concept of a balance between [[OrderVersusChaos Law and Chaos]] is bullcrap.
** You have to do this in ''VideoGame/ShinMegamiTenseiIIINocturne'' if you take the Neutral path, in order to stop your friends from bringing their selfish ideas of paradise to reality. Or, in fact, if you take any other path. You can't be allied to both Chiaki and Isamu after all, you'll have to fight at least one of them.
** In ''VideoGame/ShinMegamiTenseiIV'', if you take the Law path, you must fight Walter, who has merged with Lucifer. Taking the Chaos path means that you have to fight Jonathan, who has merged with the angels. Taking either side causes Isabeau to attempt to stop you on behalf of humanity. Either way, you'll wind up killing half of your old fellows by the end of the game.
** In ''VideoGame/ShinMegamiTenseiIVApocalypse'', Dagda eventually reveals to you that his plans for overthrowing YHVH's rule and instilling you as the new creator god involve killing everyone who believes in gods, [[GodsNeedPrayerBadly in order to kill those gods]]. Yes, you can choose to go along with his plans instead of opposing him. The first people on the chopping block? Six of the seven companions[[note]]Asahi's soul is in captivity during this particular event[[/note]] who have been traveling around Tokyo with you.
* In ''VideoGame/ValkyrieProfileCovenantOfThePlume'', the titular feather is used to sacrifice party members, but it will ''only'' work on people who already trust you as a friend. So they ''have'' to like you for you to kill them.
* ''VideoGame/SilentHillHomecoming'' has this as the first of two choices (or three, depending on which ending you're going for) that [[MultipleEndings determine the ending you get.]] Alex's mother is strapped to a device that is about to rip her apart, and you are given the choice to either end her life or try ([[CruelAndUnusualDeath and fail]]) to get her out. [[MercyKill Shooting her]] leads to a [[BittersweetEnding somewhat happier]] ending.
* Used all over the place in the ''VideoGame/DeptHeaven'' series:
** In ''VideoGame/RivieraThePromisedLand'', the trope is zigzagged, with a huge deal made out of how Ein is going to have to fight his mentor and best friend Ledah; the player is made to expect this trope. The battle leaves Ledah badly injured and asking for a MercyKill, but Ein refuses on the grounds of no way is he doing that to a friend. Shortly after this, Ledah does die, but it's at the hands of an enemy character after all.
** ''VideoGame/YggdraUnion'' has quite a lot of these--you are forced to kill the sympathetic queen of the Undines, either Roswell or Rosary (both of whom are otherwise recruitable), and a lot of innocent Bronquian civilians; in each case Yggdra and company are left wondering whether this is really the right thing to do. On top of that, there are three ShootTheDog fights--against the Verlaine ruler you killed and Kylier after they CameBackWrong, and Gulcasa, maddened by grief and about to unwittingly trigger TheEndOfTheWorldAsWeKnowIt by [[DrivenToSuicide very literally]] [[HeroicSacrifice sacrificing himself]]. The last three especially are infamous TearJerker moments.
*** There's also quite a bit of this in ''VideoGame/BlazeUnion''--C route gives us the quintessential CameBackWrong fight with Jenon, and the bad end of the B route has OmnicidalManiac Emilia in need of [[StakingTheLovedOne staking]]. The A route ''tries'' to pull this when Medoute [[FantasticRacism concludes that Gulcasa has become a monster]] and decides to [[EtTuBrute take him down herself]], but Gulcasa [[DefiedTrope gives this trope the finger]] and [[TurnTheOtherCheek spares her]], despite being told in no uncertain terms that this is [[KillHimAlready incredibly dangerous]]. As this proves his humanity, however, Medoute and Jenon leave the country instead of going after him again.
** ''VideoGame/KnightsInTheNightmare'' has Willimgard unwittingly kill his own son, who's been turned into a werewolf, and later the now-harpy Pisce as well. The narrator [[WhatTheHellHero calls him out on the latter]].
** ''{{Gungnir}}'' zigzags the trope much in the same manner as ''Riviera'', but ultimately averts it [[DarkerAndEdgier against all odds]]: despite the huge, dramatic battle between Julio and [[MoreThanMindControl Ragnus]], Julio doesn't kill his brother at the end of it, and after a lot of [[WasItAllALie yelling at the party]], Ragnus gets up and walks away.
** ''VideoGame/GloriaUnion'' features three of these fights--Ishut against his childhood [[TheRival frienemy]] [[CameBackWrong Velgas]], Elisha and Zazarland against Elisha's mother [[WellIntentionedExtremist Enryetta]], and Ishut versus his badly-abused twin brother [[PsychopathicManchild Ashley]]. Despite this being a LighterAndSofter game, the trope is played straight every time.
* ''Very'' prevalent in ''VideoGame/TalesOfSymphonia''. Let's see...
** It's part of the backstory of four members of the main cast for similar reasons (we play Lloyd and Genis as they're made to kill Marble, [[spoiler:Regal killed his lover]] and [[spoiler:Kratos killed his wife]].)
*** The fight with Marble does this weird [[spoiler: after the fight, Marble (who looks like a monster, and nothing like her original form) seems to be in much better shape then Lloyd and Genis. The only time she seems to be in any sort of pain is when she struggles to take back control of her body (which is when Lloyd and Genis learn who she is). After saying her goodbyes, she latches onto Forcystus and [[TakingYouWithMe explodes]]. Despite Magnius' insistence that they killed her (who at the time is trying to turn Marble's granddaughter against the party, by leaving out details like that fact that Marble was turned into a monster with no control over her body, and therefor is an even less reliable source of information then normal), that might [[SubvertedTrope not be the case]].]]
** In an alternate route, it's possible to fight and kill [[spoiler:Zelos]] - very close to one member of the cast (who mourns him) and a character many [[PlayerPunch players adore]].
** Less prominently, [[spoiler:Yuan]] is fighting to prevent the resurrection of his fiancée.
** Subverted when Lloyd has to fight [[spoiler:his father, who fully intends to die but ends up saved against his will.]]
** The last boss battle is against [[spoiler:Mithos in child form]] and you can have [[spoiler:Genis]], who befriended him, [[VideoGameCrueltyPotential join in the fight]].
** And in the [[VideoGame/TalesOfSymphoniaDawnOfTheNewWorld sequel]], the last two boss battles are [[spoiler:Emil VS Richter, in which Emil has always [[HoYay idolized]] Richter and looks exactly like Richter's dead best friend]], then [[spoiler:Emil VS his crush Marta and friend Lloyd]], which is also a very effective and unexpected PlayerPunch since [[spoiler:Marta was the only other permanent member of your party for the entire game, and Lloyd is the hero of the first game]].
* In ''VideoGame/GrandTheftAutoSanAndreas'', CJ is forced to kill [[spoiler: his childhood friends Big Smoke and Ryder after they betray the Grove Street Families gang to side with their rivalry gang, the Ballas. He feels genuine remorse for killing them both]].
* ''VideoGame/InFAMOUS 2'''s evil ending has Cole do this to [[spoiler:Nix and [[TearJerker Ze]]ke]]
* ''VideoGame/Left4Dead'': In Zoey's backstory, she shot her father so that he would not become infected after being bit. However, It's heavily implied that he was a carrier (immune), but Zoey couldn't have possibly known this...
* Imaginary!Barry in ''VideoGame/AlanWake''[='=]s second DLC "The Writer" lampshades this with the line "'kill your darlings'" as Alan goes to the Cabin for the final battle.
* In ''VideoGame/KnightsOfTheOldRepublicIITheSithLords'' Darth Sion tries to kill the Jedi Exile regardless of gender, but if the Exile is female he will explain that the BigBad of the game is (at least partially) the cause of his current status as a more or less corpse and part of the reason he's trying to kill her is to spare her the same fate.
* ''VideoGame/DragonAgeII'' is madly in love with this trope. In the prologue, Aveline is forced to kill Wesley, her husband, to save him from the Darkspawn taint, unless Hawke does it for her. Later on, Anders has the choice between either killing [[spoiler: his ex-lover Karl, or leaving him to remain Tranquil, which he and Karl both regard as a FateWorseThanDeath.]] Hawke may be forced to [[spoiler: MercyKill a tainted sibling]], and Merrill may have to kill [[spoiler: her mentor and adoptive mother, Keeper Marethari, as well as potentially her ''entire clan''.]] Varric ends up having to either [[spoiler: MercyKill his brother Bartrand, or spend the rest of his life caring for him as he has been driven completely insane by the idol (after Bartrand tried to kill him).]] Fenris may kill [[spoiler: his sister, in revenge for betraying him to his former master.]] And in the endgame, Hawke may [[spoiler: kill his/her lover, if s/he romanced Anders and chooses to kill him after he blows up the Chantry.]] [[UpToEleven Damn.]]
* ''VideoGame/BlazBlue'': After her love interest, Lotte Carmine, [[BodyHorror lost his body]] [[GoMadFromTheRevelation and his mind]] and turned into [[TheWormThatWalks Arakune]], [[AnimeChineseGirl Litchi Faye-Ling]] set out to either cure him of his condition, or put an end to him, should that prove to be an impossible task, though no conclusion has been reached yet. The developers play this for heartwrenching drama in the canon continuty, but aren't shy to play it for laughs everywhere else.
* ''VideoGame/TheWalkingDead'':
** Clementine may do this to Lee to prevent reanimation and as a MercyKill before he completely succumbs to the bite.
** [[spoiler:Duck]] gets bitten by a walker, forcing everyone to kill him before he turns into a walker. Katjaa tries to kill him herself, but can't do it and shoots herself. Then you get to choose to let Kenny shoot him, or do it yourself.
** At the end of Season 2, [[spoiler:Clementine forced to either stop an enraged Kenny from killing Jane by shooting him or look away and let him finish the job]].
* In one ending of ''VideoGame/HyperdimensionNeptuniaMk2'', Nepgear has to kill all the other [=CPUs=] and Candidates, or those she can't bring herself to kill [[DrivenToSuicide do it for her. None of them die quickly. ''At all''. Have fun listening to a couple of ''children'' hysterically scream they don't want to die as they slowly expire in excruciating pain.]]
* In ''VideoGame/WarCraftIII'', at the end of the Human campaign, Arthas becomes a Death Knight and kills his father.
* In ''VideoGame/TheWorldEndsWithYou'' [[spoiler: Joshua]] tries to invoke this by telling Neku that if he [[spoiler: Shoots him, that he'll give him the job of Composer. Luckily for both of them, Neku refused to do this, and it was just a test]]
* ''Franchise/BreathOfFire'':
** In ''VideoGame/BreathOfFireI'', [[TheProtagonist Ryu]] and his friends are forced to fight and kill his sister Sara, who has been {{Brainwashed}} by [[TheStarscream Jade]].
** In ''VideoGame/BreathOfFireIII'', the team eventually is confronted by Teepo, Ryu and Rei's adopted sibling from the beginning of the game, now on the BigBad's side. He does attempt to remove Ryu's powers non-lethally, but being unable to convince him to surrender them he resorts to a fight to the death. Suffice to say, Rei is devastated the remainder of the game.
** Perhaps the most heartbreaking one occurs in ''VideoGame/BreathOfFireIV'', where [[spoiler:Cray has to perform a MercyKill on Elina, his sweetheart he's been looking for all over the world, at her request due to the horrible experiments [[MadScientist Lord]] [[MagnificentBastard Yuna]] performed on her.]]
* In ''VideoGame/{{Tenchu}} 2: Birth of the Stealth Assassins'', Ayame is faced with having to fight Tatsumaru, a former Azuma ninja and her crush, and kill him in battle after his betrayal and subsequent raid on the Azuma Village.
* In ''VideoGame/FinalFantasyTactics'': [[spoiler:Ramza]] [[MercyKill is forced to kill]] [[spoiler:his brother Zalbaag, who has been reanimated as a vampire by Folmarv and [[ICannotSelfTerminate as he can't control his own body, pleads for death]]]].
* ''VideoGame/FinalFantasyX'': Invokes this one hard. Summoners make a pilgrimage across Spira to gather Aeons and prepare for a battle against the world-destroying entity Sin, accompanied by their closest friends as Guardians. This gives the world a period of Calm before Sin inevitably comes back and the process has to start again with another Summoner. Everyone but Tidus knows that the Summoner ''always'' dies at the end of their pilgrimage while facing Sin. Worse, Lady Yunalesca lays out the way to do it - the Summoner must make a HumanSacrifice of one of their Guardians to make an Aeon. And ''even'' worse, that new Aeon will become the next Sin. But leave it to Tidus to ask all the wrong questions, Yuna to refuse that option, and [[MagnificentBastard Auron]] to engineer the ''perfect'' circumstances to make ScrewDestiny a valid option. [[spoiler: The fact that Tidus's estranged father is the current Sin also makes the final BossBattle this trope.]]

[[folder:Web Original]]
* This trope is ''Roleplay/SurvivalOfTheFittest'' to a tee. Particularly, in V2, Bryan Calvert has to MercyKill his best friend, Seth Mattlock, en route to to fighting Mariavel Varella, a former friend turned psycho.

[[folder:Western Animation]]
* In the fourth season finale of ''WesternAnimation/{{Archer}}'', Sterling, Lana, Ray, and Cyril are all trapped in an underwater base and have to make a long swim to safety, and there's only three wetsuits. To save the rest of the team, [[spoiler:Archer offers to let one of the others drown him, with the expectation that once they reach the escape vehicle, they can revive him. Lana does the honors, and finds it a lot harder than she expected]].
* In ''WesternAnimation/{{Danny Phantom}}'''s MadeForTVMovie ''WesternAnimation/{{TheUltimateEnemy}}, [[spoiler: Danny has grown up to be an OmnicidalManiac, and upon meeting his past self and [[FutureMeScaresMe upon seeing his existence is in jeopardy]], goes back in time to set in motion the events that led to his current state: The death of everyone he loves. [[EvilFeelsGood He's darn happy about it, too.]]]]
* In the season 8 finale of ''WesternAnimation/{{Adventure Time}}'', Finn [[spoiler: accidentally kills his grass duplicate Fern after Fern attempted to [[CaptureandReplicate trap Finn in a dungeon and take over his life]] not long after he confessed to Fern that he saw him as a brother.]]

[[folder:Real Life]]
* Saddam Hussein would order his bodyguards to kill members of their family, so they would "have nowhere to run."
* In seppuku, the role of the ''kaishaku'' is to behead the man who has just committed the act. It was usually filled by a friend, or at least a loyal servant. This likely formed because seppuku, being a suicide ritual in which you stab yourself in abdomen and cut left from right, would otherwise bring about an incredibly painful end. The exact time to behead varied and was discussed between the principal and kaishaku beforehand - while initially the beheading was performed after stabbing themselves and cutting horizontally, it changed as time went on to that they may be beheaded as soon as they stab themselves before they can even show pain from it, or even just showing they intended to go through with it by making a motion toward grabbing the suicide blade.
* This is the (incredibly twisted) logic when it comes to some cases of PaterFamilicide (or any variant thereof), where the killer does so because they firmly believe that their family is better off dead.
* Nazi Propaganda minister Joseph Goebbels and his wife Magda committed suicide in 1945 because it was clear that the war was lost. Before doing so, they made all their six children swallow cyanide pills so they could die too.
* Japanese criminal Sade Abe strangled the man she loved to death while having sex. Afterwards she cut of his penis and carried it with her. Her morbid lust story later inspired the film ''Film/InTheRealmOfTheSenses (1976)''.
* Obsessive stalkers can also cross into this territory.
* Music/JohnLennon was presumably shot by a man who claimed to be his biggest fan.
* The "merciful death" version of this is the reason many people have elderly or terminally ill pets put to sleep, and is a major driver behind the "death with dignity" movement, which fights for terminally ill people's right to die on their own terms.