I shook my head.
"Will," he said. "The belief, deep down, that they know what is right and that they'll see it done."
"So tell me, Catherine Foundling," he murmured, his voice smooth as velvet. "What do you think is right?"
He spun the knife so that the handle faced me, the touch of his fingertips deft and light.
"How far are you willing to go, to see it done?"
Anti-heroes and villains can see killing as a necessary if distasteful step in reaching their goals — they may have even carefully planned out their first kill with a great deal of thought put into whether the target genuinely needs to die. The reasons they give for this and the amount of anguish they go through before deciding can also say a lot about the character.
In this context, the willingness to kill is used to show that they are fully committed to their cause. An actual death is not necessarily required as long as the protagonist decides that killing for their cause is justifiable. Usually, this is for simple pragmatic reasons — some villains either just can't be held, or there is no authority that would or could arrest them. So the only way to stop them from either blocking your way or harming other people as soon as your back is turned is, well, to kill them. Angst afterwards is fine — they have just killed someone, after all — as long as they ultimately decide that the act was justified.
Note that it is their mental state and decision that is key to this trope — 'someone who kills people' is not valid unless we see them choose to kill or explain their reasoning. It is a popular event to show in flashbacks, for those characters who don't begin with an origin story.
- Darwin's Game: Kaname Sudo is inadvertently forced into a killing game where he tries to go against its "kill or be killed" dogma. When he first started out as a D-game player, he bent himself into pretzels to avoid killing others, even being reluctant to open fire on Eighth when they came at him in massive numbers. Then Wang goes and sadistically tortures a close friend of his to death. Well, no more Mr. Nice Guy.
- Death Note: Light's first two kills serve as this. The first guy Light kills is a serious headcase who had taken a school full of kids hostage. Light writes the guy's name into the title notebook as a means of figuring out whether or not it was real or just a sick prank. When the criminal in question dies of a heart attack 40 seconds after Light wrote the name in, Light still isn't completely convinced that the Death Note is real, so after school, he decides to test out the notebook a second time, taking out the leader of a motorcycle gang and stopping his Attempted Rape of a young woman by sending him and his bike into the path of an oncoming semi. After wrestling with the implications of passing judgement upon people like this, Light makes the decision to become Kira and "change the world" by killing off its criminals and evil people, which sets him on the path to developing his infamous god-complex and becoming the Villain Protagonist of the series.
- In Digimon Adventure, the heroes were forced into do or die situations so often that they would kill when they had to. However, in the sequel series the first few seasons the new members only fought mind control victims (that they freed) and artificial control spire enemies which they had no problems destroying since they weren't real. Towards the end of the series, all three of the new recruits this season are forced to kill at least one real enemy, which shakes them up.
- Dragon Ball: Gohan, while being in several life or death fights throughout the series where he usually acted on instinct (and was never powerful enough to kill enemies on his own outside of filler arcs), was faced with the decision to consciously kill Cell during the Cell games. Despite being brutalized by Cell and watching him torment all the other Z fighters and threaten the planet, Gohan doesn't gain the will to kill until Android 16 reaches him. He explains that people like Cell will never listen to words, and that Gohan must kill Cell in order to protect everything he loves. Unfortunately in the process he also gains the will to torture and decides to punish Cell for everything he's done, which leads to Goku needing to commit a Heroic Sacrifice after Cell decides to self-destruct in order to take out the entire planet.
- Madlax: The Actual Pacifist Vanessa has trouble coming to terms with shooting a guy to protect Madlax until the latter confirms that she only wounded him. Still, this leads to quite a bit of Character Development in Vanessa, who eventually asks Madlax to teach her to shoot properly.
- Uso Ewin of Mobile Suit Victory Gundam has this going on as the series progresses. He's horrified at his first kills, but after an encounter after a Punch-Clock Villain who essentially tells him that he can't avoid killing people in a war, he starts gradually losing his qualms about killing enemies.
- The Moriarty brothers all have to go through this process in Moriarty the Patriot.
- Albert mentions vomiting after his first murder
- William didn't even want to pickpocket people in the first chapter.
- ...Okay, maybe Louis was always down with murder. But probably not, given that he shakes it off pretty quickly and with prejudice later.
- In episode 8 of Puella Magi Madoka Magica, this happens to Sayaka when she brutally attacks and possibly kills two sexists on a subway. She had come to the realization that if she is going to be a proper hero, unlike Kyoko and Akemi, and hunt witches for the sake of protecting humans, then why stop at the witches? It's around this point where she becomes Oktavia von Seckendorff and lets go of her humanity.
- Villager A Wants To Save The Villainess No Matter What: Allen refusing to kill bandits on an Escort Mission gets him chewed out by his Adventure Guild master about how said bandits will just commit more crimes, and indeed the bandits kidnap some girls the next day, which makes Allen regret his decision and kill bandits on his way to rescue the girls.
- In Yu-Gi-Oh! GX, Adrian Gecko finds Exodia in a sealed chamber, and in order to obtain Exodia's power he decides to use his love interest Echo as a sacrifice, so he can become King of the alternate dimension and create a world void of poverty.
- Captain Britain: Brian Braddock was a fairly straightforward example of The Cape... until the day his nemesis, Slaymaster, fought Brian's sister Betsy and beat her to within an inch of her life before ripping out her eyes. Slaymaster's last words — spoken as Brian Braddock stood over him, holding a large rock — were: "Fool! You have not the strength to kill..."
- Invincible: A major part of the titular superhero's Character Development entails him gradually abandoning his Thou Shalt Not Kill attitude and becoming significantly less antsy about killing especially dangerous supervillains after multiple bad experiences teach him that some villains are just too deadly to be taken alive practically and may also take advantage of his mercy to do more harm, as well as that holding back in some fights can get him and others killed. The biggest tipping point comes when his archenemy Angstrom Levy gets thousands of people killed with one of his attacks, with Mark directly acknowledging that Levy would never have gotten the opportunity to do it if he hadn't been killed when Invincible had the chance. From that point on, Mark not only has zero hesitation about killing villains if he absolutely must ("absolutely must" being the key words), but defaults to lethal force in future encounters with Levy.
- Spider-Man: Symbiote Spider-Man establishes that when Mysterio started out as a supervillain, he never meant for anybody to get hurt or killed, and actually tended to go out of his way to avoid injuring people — especially civilians — too badly in his schemes. When he kills for the first time by inadvertently causing the death of a bystander in a bank robbery gone wrong, he's so horrified, upset, and traumatized by the experience that he considers leaving crime. A vicious beating from a symbiote-influenced Spider-Man puts the kibosh on his retirement plans and the ensuing decades of living the criminal lifestyle plus learning he's dying of cancer (and then coming back thanks to an ill-advised Deal with the Devil) causes him to slowly lose his aversion to violence and become frighteningly willing to kill to get what he wants, even if he still doesn't actively seek it.
- He goes through similar in Webspinners: Tales of Spider-Man, where he seems genuinely upset for a time at seemingly killing someone—only to shove down the "guilt and shame" and embrace his supervillainy completely.
- Watchmen: This was a major sign of Rorschach having transformed into his current persona - up until that point, he had only beaten criminals up and tied them up for the police. However, after finding that a kidnapped child had been chopped up and fed to the kidnapper's two Alsatians, he begins to kill villains as necessary.
- In Desperation Attracts Vultures a big part of the Chuunin Exam arc is Naruto's unwillingness to kill someone, especially if he's already beaten them. This comes back to bite him when Ino dies against an enemy Naruto thought he'd beat. Later, when facing Gaara, Naruto still hesitates until Gaara tries to kill Hanabi; at which point Naruto kills him.
- Guardians, Wizards, and Kung-Fu Fighters: When Nerissa killed Yua the Banshee by mistake, she was horrified. A year later, having thrown herself into her studies and grown into a Knight Templar, she slaughters the Great Barons of Creznac without a second thought.
- Harry Potter and the Methods of Rationality: Harry Evens-Verres crosses this line during a battle with a mountain troll, and a close friend is mortally wounded. This causes Quirrel to note that they had "just discarded [their] foolish little reluctances". They kill the thing that was attacking, and later coolly plans the murder of Lucius Malfoy if he refuses his offer to form an alliance, as he will otherwise remain an enemy.
- Silently Watches' fanfictions typically involve a hero who (among other things) does not kill in canon deciding to do so.
- Raven in Coincidence and Misunderstandings, who accepts her demonic heritage as a part of herself and subsequently becomes darker in mind and body - this is marked by her decision to mentally kill Dr. Light via Go Mad from the Revelation at the story's end to prevent him from harming anyone else, though she regrets this when she realizes that the Titans wanted to interrogate him.
- In Mastermind: Strategist for Hire, Izuku stabs Glimmer, one of Uwabami's Sidekicks, to death to prove to himself that he has the will to carry out his villainous plans himself, rather than rely on other villains to carry them out.
- Megami no Hanabira: Played with: while the girls have no issue killing demons, they find themselves forced to take more and more violent action against their ever-mounting number of human foes. It culminates when Sara kills Brother Chick: even though she had no conscious intention of doing so, her Fiend picked up on her murderous feelings and did what she wanted to do to Chick deep down. By the time they confront Father Phillips, the one who ruined their lives and destroyed their city, they're fighting to kill, only sparing him when the realize that imprisonment would hurt a man with a god complex far more than simply killing him.
- Vow of Nudity: An ongoing flashback in one story chronicles an imperial slave being kidnapped by a platoon of imperial soldiers and pressed into service on the front lines. Though she starts the story meek and obedient, by the end of their harrowing and deadly encounters with local wildlife she eventually snaps the neck of the last surviving soldier and finds the courage to flee the empire seeking her freedom.
- Vow of the King: Yoruichi forces this upon Orihime in training, making it look like she'll kill Tatsuki if Orihime doesn't kill her.
- In Alice in Wonderland (2010) Alice's biggest reason for not wanting to fight the Jabberwok is part doubting she can, and doubting she could, telling Absolem she doesn't know if she could if her life depended on it. He assures her it will depend on it, but also says she can, as all she really needs to do is hold the Vorpal Blade so it can kill the villain.
- Batman Begins. After he has trained with the League of Shadows, Bruce's mentor asks him to do this as a show of his commitment after his last test. Namely, executing a prisoner who killed a fellow farmer for his land. This, the mentor says, is justice and balance and will prove that Bruce will do what is necessary in the field. Needless to say, the future Batman refuses, causing said mentor to later remark on his lack of 'courage to do all that is necessary' in comparison to himself and his plan to destroy Gotham to scare the rest of the cities in the nation into reforming. Towards the end, Batman does get Ra's at his mercy, and is asked again whether he now had that courage. He doesn't kill Ra's, but instead leaves him to die in the derailing monorail that he himself had set in motion.
- In A Blueprint for Murder, having exhausted his legal options, Cam decides that the only way he can save his nephew Doug from his stepmother Lynne is to poison her. He balks at his first attempts and throws the poison overboard. However, on finding what he believes to be a poison tablet in her luggage, his will strengthens and he drops it into her cocktail.
- In Casino Royale (2006), Bond's discussion with Dryden (with flashbacks to a brutal fight between Bond and Dryden's contact) has shades of this. To be promoted to double-0 status, an agent must kill two people. The contact was Bond's first; the second is easier; considerably easier.
- Wolves: The first time Cayden fights Connor and his pack, he's actively trying not to kill, with the result that he gets his ass handed to him and nearly dies. The second time, he's learned, and employs a healthy does of Combat Pragmatism. His opening move is to kill the sentries by sneaking up and slashing their throats.
- The Alex Rider series plays with this. While the villains usually end up dead, and mostly because of Alex, he rationalises them away as accidents (in that he didn't intend any of them to die or directly have a hand in their deaths). Alex's willingness to kill is treated by the story as a Moral Event Horizon that he has no intention of crossing. In Scorpia, when the titular organisation manipulates him into trying to kill Ms. Jones by showing her ordering his father's death, Alex still has trouble shooting. Eventually, he does shoot, but later is told that his shot would have missed despite being at point-blank range, meaning he really can't kill. In Crocodile Tears, Alex begins to lose this innocence, doing things that would definitely kill the recipients - he cuts open a mook's protective suit while in a toxic biodome, and attaches an explosive to a barrel before rolling it over to the main villain. Finally, in Scorpia Rising, he shoots Hugo Grief point-blank in the head while the former was at his mercy. Unusually, this is treated as a good thing, kind of. Ms. Jones states later that due to Julius' personality and appearance, Alex also symbolically killed off the part of his mind that MI5 created - in other words, the part that killed Julius in the first place.
- This was how Amadeus recruited Catherine in A Practical Guide to Evil, as seen in the page quote - he catches her in the hands of rapist and murderer, and informs her that Imperial law would merely see them imprisoned for five years. He then tells her that there is another way, and offers her his knife as a test of her resolve. Afterwards, he tells her It Never Gets Any Easier, which she later regards as a very kind lie.
- In A Brother's Price, Jerin gains the will to kill when after he was kidnapped, his rescuer is almost killed by the kidnappers. He doesn't like it, but makes no resolution to not do it again, either.
- In Dragon Bones, sweet, Cute Mute Ciarra witnesses a group of bandits about to rape a girl. Even though Ciarra's brother told her to stay out of combat, she goes after one of the bandits, wounding him lethally. It's downplayed in that it's her brother, Ward, who actually kills the man, as Ciarra apparently didn't have the nerve to witness the actual death of the man.(Or she just wanted him to suffer ... as she doesn't talk, that's not quite clear. She's a bit upset afterwards) Her brother Tosten doesn't fare much better, but they both get used to the bandit-hunting after a time.
- A Feast for Crows: Brienne goes through this before killing her first man (in self-defence), questioning whether she has the strength to take a life. Ultimately, it gets easier for her but she still doesn't enjoy it. It helped that her Old Master was worried this would be a Fatal Flaw, so had her slaughter animals at a butcher to desensitize her to killing.
- This makes up a significant part of Kyoshi’s character arc in the Avatar universe tie-in novel, The Rise of Kyoshi. After Big Bad Jianzhu kills her Parental Substitute Kelsang and friend Yun, she sets out to learn enough bending to kill him in revenge. She’s come to peace with killing a corrupt governor only to find out he’s just a kid who’s not much younger than she is. She lets him go but makes it clear that if he doesn't get his act together, she will kill him. She kills a man by the name of Xu in a duel. When she and Jianzhu meet again, she’s fully ready to kill him until her friend Yun comes back from his presumed death and beats her to the punch.
- Rogue Angel: A number of times, Annja Creed ruminates about the killing she may need to do, preparing herself for the act.
- In Sharpe's Waterloo, Lord John Rossendale is an inexperienced braggart who's terrified when Sharpe first confronts him, but on the battlefield of Waterloo he learns how to become a killer. Not that it helps him, since he doesn't survive the battle.
- Deconstructed in A Frozen Heart, a Tie-In Novel of Frozen (2013) which depicts Prince Hans's life before the film's events. As a child, he was mocked by his family for his unwillingness to murder people, especially since his kingdom is a totalitarian dictatorship. Having had enough of it, he decides that if he wants to win their respect, then he'll have to accept any task they give him, even if it involved violence against their subjects, but it also changes him into a ruthless man incapable of bonding with others as he's trained himself to remain detached in order to make the killing easier to reconcile. Fast forward three years later, by the time he's in Arendelle, he's so desensitized that he resorted to his family's tactics in order to become its ruler, despite having vowed not to use them originally.
- Breaking Bad:
- Walter White agonizes over whether or not to kill Krazy-8 in the first season, drawing up a literal "pros and cons" list. As the series goes on, Walter becomes much more comfortable with murder.
- Jesse Pinkman does not want to kill Gale at all, and when he's got the chance, he spends over a minute pointing the gun at him in tears before finally pulling the trigger. As opposed to Walter, Jesse never quite gets over it. Like Walt though, Jesse does get comfortable with murder as well, killing 2 more without any sort of Heroic BSoD during the series.
- In Buffy the Vampire Slayer, this happens to Faith after she first kills another human being (as opposed to a soulless and Always Chaotic Evil vampire, demon, etc.) The kill itself is unplanned; she lashes out thinking the man is a vampire. It is her subsequent justification of the act—that the man was expendable, collateral damage—that indicates the beginnings of her Face–Heel Turn and her subsequent killing of more innocent people.
- In Star Trek: The Next Generation, "The Most Toys," Kivas Fajo kidnaps Data, keeping him in a cell that Data cannot hack or break his way out of, and wears a belt that emits a force field preventing Data from physically touching him. Eventually, Data escapes with the help of a henchwomen, who finally understands despite years of loyal service, she is very much expendable. Before they fully get away, Fajo catches them and uses a brutal disruptor to kill the woman. Fajo then turns to Data who is armed with a similar disruptor. Data demands that Fajo surrenders, but Fajo refuses and explains that he will kill as many people as necessary to make Data do what he wants, certain that Data's programming prevents him from killing him instead. Data, however, calmly considers his options for a moment. As Fajo has showed a willingness to kill and has threatened to do it again, he presents a clear and active threat to others, so for Data there is absolutely no question that he has a moral obligation to stop Fajo. But Fajo has showed a complete unwillingness to be reasoned with and has actively refused to surrender, and Data cannot physically subdue him due to the force field. With all this in mind, Data concludes that there is only one logical and moral way to resolve this dilemma:
Data: I cannot permit this to continue. (aims disruptor at Fajo)
- In fact, the only thing that saves Fajo is that Data was beamed out right as he pulled the trigger. The transporter chief informs the others that the disruptor was actually in a state of discharge, and had to be deactivated before materialization. Data uses Exact Words ("Perhaps something happened during the transport") to avoid admitting or explaining that he was trying to kill someone (even justifiably).
- In Hamlet, this is one interpretation of Hamlet's character when he stalls after being called to avenge his father's murder. At one point he rants about how he's standing around talking about killing the murderer rather than actually doing anything:
"Why, what an ass am I! This is most brave,
That I, the son of a dear father murdered,
Prompted to my revenge by heaven and hell,
Must, like a whore, unpack my heart with words
And fall a-cursing..."
- Sweeney Todd: The Demon Barber of Fleet Street: The eponymous Sweeney Todd was originally a wronged man looking to get his daughter back from an evil judge who abducted the girl after raping Sweeney's wife and sending Sweeney himself to Australia on a trumped-up charge. That and kill the judge and his right hand man for taking everything from him. That changes when a charlatan named Pirelli recognizes Sweeney as an escaped convict and threatens to turn him in, driving Sweeney to kill him. Sweeney has never killed before, but he shows no remorse for this act, deciding it was necessary to protect his cover. Sweeney finds he has no qualms about continuing to kill, and launches himself into a frenzied campaign of revenge against the world that wronged him by becoming a Serial Killer and handing the bodies over to his friend Mrs. Lovett for, er, disposal.
- In the Burial at Sea DLC of Bioshock Infinite, Daisy Fitzroy's apparent attempt to murder a child is revealed to have been act set up by both her and the Lutece twins in order to force Elizabeth to mature through spilling blood, and thus the will to oppose Comstock.
- The main plot point of Jason Brody's Character Development in Far Cry 3. Initially, Jason is just a sheltered rich kid taken captive by Ruthless Modern Pirates who wants to save his family and get off the Rook Islands. The first pirate he kills traumatises him, and he's reluctant to accept money from Dennis to buy a gun, knowing he'll end up killing more people with it. Shortly after that, though, he stops worrying about killing pirates, and he actually starts liking it. This is deconstructed, as he's also going through increasing Sanity Slippage, and, depending on which ending you pick, costs him the life of his friends and family, and his own life at the hands of Citra.
- This is part of Luke's Character Development in Tales of the Abyss. Originally a Sheltered Aristocrat, he is thrown into a high-stakes adventure where fights to the death happen frequently. He discusses this with his party members and the conclusion is basically that killing is, unfortunately, necessary (incidentally, all of them at that point were soldiers). This is the point where Luke canonically starts seriously fighting human beings instead of just monsters.
- Deconstructed in Injustice: Gods Among Us. After killing the Joker in revenge for nuking Metropolis and the death of his wife Lois, an alternate version of Superman snaps and takes a hardline approach to solving crime. Part of the conflict between him and Batman is him breaking of the Thou Shalt Not Kill rule. As time passes, he accepts killing for justice, but he also Jumps Off The Slippery Slope, transforming him into an Ax-Crazy, raging maniac who reacts with outright brute force when others call him out on his actions. The way he kills Shazam and Lex Luthor in a cold-blooded manner, and unleashes his thugs to quash any dissent against his rule shows the ruthless monster he's now become, a far cry from the idealistic hero he once was.
- The narrator of the autobiographical Joe vs. Elan School discusses this at multiple points, and it's borne out of his abuse at the titular school. The first time, there's a possibility that another inmate will rat Joe out and prolong his stay; Joe prepares himself to go into berserker mode to harm as many people as possible in order to possibly be seen as a liability and kicked out, but he never gets to that point since the other kid doesn't rat on him. Later, after Joe leaves the school for good and comes home, before he goes to bed each evening, he starts keeping a baseball bat within arm's reach, as well as a lighter and a can of hairspray. As he says, "I didn't want to burn someone to death, but murder was definitely on the table if anyone ever, EVER tried to take me against my will again."
- Dr. Horrible's Sing-Along Blog: This occurs to Dr. Horrible after Captain Hammer tells him that he is dating Penny, Horrible's crush, purely to spite him. This causes Horrible's hatred for Hammer to overcome his previous reluctance to kill, and in Brand New Day openly plans to kill him. In the end, Horrible can't bring himself to kill Hammer before the latter gets free, but his plan ends up accidentally killing Penny. His final state depends on your interpretation of whether he has crossed the Moral Event Horizon or not by the end.
- Rasa: In order to protect the secret of her attempted escape, Jova overpowers Ya Gol Gi, takes his tabula, and commands him to stop breathing. The murder is a defining moment of Character Development for her as she matures to match the brutality of the Crapsack World she lives in.
She felt no pity, no regret, and no remorse. Only triumph.
- Worm: Skitter first uses lethal force to try and kill Coil, though she admits that he likely has an antidote to her spiders' venom. Later, however, she does end up executing him.
Coil: You're not a killer.
Skitter: No... but I suppose, in a roundabout way, you made me into one.
- An episode of Justice League involves an Alternate Universe version of the League called the Justice Lords. At the beginning, we see a flashback showing that Earth's Superman make this decision and kill Lex Luthor at Luthor's goading because he killed The Flash and caused another World War. After that the Lords has no problem killing (or lobotomising) criminals, justifying it as the greater good. They proceed to form a ruthless dictatorship across Earth, punishing even small crimes harshly. Interestingly, Lord-Superman lobotomizing every Super Villain winds up biting League-Superman in the ass when he does it to Doomsday, the monster that becomes stronger every time you kill him. Doomsday later comes back with a grudge against Superman (albeit the wrong one), and he tries Lord-Superman's tactic only for him to find that his skull has become far more durable in the meantime.
- In the fifth season of Samurai Jack, the titular samurai kills one of the Daughters of Aku by slitting her throat. Up until that point, Jack assumed they were robots, until he saw the assassin's blood. In the next episode, Jack debates his options, but ultimately decides "it's kill or be killed." When Jack encounters the Daughters again, it's a fight to the death.
- Part of Jim's early development in Trollhunters is him learning how to kill, after openly defying the Trollhunter's second rule ("Always finish the fight.") by refusing to kill his first two opponents.
- Subverted by Avatar: The Last Airbender. In the final season, Avatar Aang grapples with potentially having to kill Fire Lord Ozai. Everything seems to lead to Aang making that choice until he discovers a different path at the last possible moment.