"... And a woman?"
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.
- 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 encourages him that in this instance it's okay before being crushed to death just a few feet away from him. This turning point pushes him into a sustained Super Saiyan 2 form for the first time.
- 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.
- 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 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.
- 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 Designated Love Interest Echo as a sacrifice, so he can become King of the alternate dimension and create a world void of poverty.
- In 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.
- 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 realises that the Titans wanted to interrogate him.
- 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.
- 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. However Bruce seems perfectly fine with killing people indirectly since in the very scene where he refused to execute an individual he blew up the building everyone was in to get away, likely resulting in more than a few casualties including the person who was tied up to be executed as well.
- 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.
- 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.
- 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.
- 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 - when SCORPIA 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 the last two books, 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, the last book 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.
- 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.
- 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.
- Rogue Angel: A number of times, Annja Creed ruminates about the killing she may need to do, preparing herself for the act.
- 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 B.S.O.D. 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.
- 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 and, 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 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..."
- 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.
- In the Burial at Sea DLC of Bioshock Infinite, Daisy Fitzroy's attempt to murder a child is retconned into an act set up by both her and the Lutece twins in order to give Elizabeth the will to kill and thus the will to oppose Comstock.
- 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.
- 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.
- 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.
- 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 Superman make this decision and killing Lex Luthor at Luthor's goading when The Flash seemingly dies. After that the League has no problem killing (or lobotomising) criminals, justifying it as the greater good. They proceed to form a peaceful but ruthless dictatorship across Earth, punishing even small crimes harshly. Superman lobotomizing every Super Villain winds up biting him in the ass when he does it to Doomsday, the monster that becomes stronger every time you kill him. Doomsday comes back to terrorize the Lords only for them to find that his skull has become far more durable in the meantime.
- 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.