Basic Trope: A character commits a very morally questionable action, and uses this as a justification after the fact.
- Straight: John commits a horrible atrocity because he thinks it will avert some worse catastrophe. When confronted about it after the fact, this is his justification.
- Exaggerated: John is in danger of being late turning in a paper for a homework assignment. He decides to run his car through a mall and runs over several people. When questioned why he did it, he states "I did what I had to do."
- Downplayed: John doesn't commit one large atrocity or horrible action, but a few smaller morally grey actions, like constantly lying to his friends and manipulating people, to avert worse situations, and justifies it to himself this way.
- Justified:
- John's actions really will avert The End of the World as We Know It, an invasion from Hell, or some other horrible fate that will befall humanity. Given the gravity of the situation, his actions are well justified.
- … and he did everything he could to not cross the line between necessity and overkill.
- Inverted: The villain, Jack, is forced to do a hugely nice and magnanimous action in order to ensure that his evil plans are carried out smoothly or prevent the world's destruction so he can take it over. He justifies it with this statement.
- Subverted:
- John considers doing something horrible, justifying it with this methodology, only to stop himself at the last minute because he can't bring himself to do it.
- John tries to commit a great atrocity, with the intention to justify it this way, only for the Token Evil Teammate to do it instead, preventing John from having to dirty his hands, and claiming that he did because he likes committing atrocities.
- Mary believes John has committed an atrocity because of this, only for John to admit he only did it because he was bored.
- Double Subverted:
- John may not want to commit the atrocity in question, but Peter is far more willing to Shoot the Dog, and does it anyway, justifying it this way.
- The Token Evil Teammate admits that he committed the atrocity because it had to be done, and he just didn't want John to dirty his hands because he sees him as a better man than him.
- John lied to Mary when he says he committed the atrocity out of boredom. He just wants the world to hate him for what he did, so he pretends he did it for no reason.
- Parodied:
- John stays outside for an entire night in order to be in line for the newest iPhone and catches Pneumonia. He justifies it to his best friend with this excuse.
- John grabs a little girl's ice cream and throws it on the ground. When she asks why, he stoically says "I Did What I had to do".
- Zig Zagged: John prepares to commit an atrocity justifying it this way. Then he stops himself at the last minute because he couldn't bring himself to do it. Only then he decides to do it anyway, only to regret doing it later and realize that "I Did What I had to do" is not a good excuse...only to then use it as an excuse later on anyway when someone calls him on it out of pride.
- Averted: John refuses to commit any kind of atrocities or actions that would necessitate this excuse in the first place.
- Enforced: The story wants to illustrate that sometimes leaders need to do morally repugnant actions for the greater good, so John will have to kick a few puppies during the story.
- Lampshaded: "Don't you hate it when people say they did what they had to do after doing something assholish, as if that makes it alright?"
- Invoked: The villains purposely setup up a situation necessitating that John the hero will have to Shoot the Dog, knowing he will claim this and that it will weaken his relationship with the other heroes who don't believe in this ideology.
- Exploited: John is made the lead hero by the Big Good because he knows that he will do what he has to do when the situation calls for it, and he needs someone with that kind of morality to get what he wants done.
- Defied:
- John is presented a situation where he could do something horrible and claim this, but actively refuses to do so and decides to Take a Third Option.
- From Jim: "I don't care how you try to phrase your excuse, you try to kill that dog and I'll end you right then and there, and whatever plan you were trying to accomplish that had "kill my dog" as a step is going to crash and burn." John decides not to do what needs to be done, or at least not do that in specific.
- Discussed: "John the type of guy that when something horrible needs to be done for the greater good, he will do it, no questions asked."
- Conversed: "He murdered all those people and his only excuse is that he did what he had to do?"
- Deconstructed:
- Even though John justifies his actions this way, his friends believe he went too far and there had to be another way. Their friendship with him falls apart as a result.
- John claims this, but he really only committed that massacre because it was more expedient than trying to cure those people of their disease. He really doesn't care about the greater good.
- Though John could claim this, he realizes that no excuse he could offer could override the fact that he did what he did, or change the fact that he did something horrible in order to avert another tragedy. He accepts the hatred of those he hurt through his actions and any legal consequences.
- John commits an atrocity hoping to avoid a horrible event from happening...only to later find out that what he did didn't stop that event from happening at all and what he did was pointless. He promptly commits suicide out of guilt
- John commits numerous war crimes in order to end a war faster, justifying it with this. However, his actions only end up embittering the enemy, prolonging the war further instead.
- John falls deeper and deeper into depravity and justifies it with this. However, it becomes increasingly clear that he's only acting to selfishly help himself and the things he's doing are motivated only by self-interest, and the audience is clearly expected to see through his justifications as self-serving excuses.
- John constantly commits evil actions, justifying it this way. As he does, It Gets Easier, and soon, he becomes a sociopath, willing to commit evil just out of convenience, whether he needs to or not.
- A survivor - of a few - of the atrocity John committed wreak revenge on John by committing it against him or his loved ones. And John - or, at least, the audience - is hard-pressed to condemn them for it. Alternatively, they work to ensure that John does not reach his goals, so that John's atrocity is pointless.
- Reconstructed:
- John's friends eventually come to accept that he really had no choice to do what he did and allow him to come back into the fold.
- Played For Laughs:
- Here's one example:
John: (Running) We have to get to the train station to stop Chase from escaping.
Lance: (also running) Look out for that puppy in front of you.
John punts the puppy 20 yards a way without missing a beat
Lance: What the hell dude!!!
John: (Stoically) We need to hurry, I did what I had to do!
Lance: You could have just ran around it!
John: I DID WHAT I HAD TO DO! - Played For Drama:
- John tries to justify doing something horrible, but truthfully, he feels horrible for what he did and suffers PTSD and horrendous amounts of guilt over his actions. His friends see him as a monster and he himself feels the same way. He struggles with depression and suicidal tendencies because of his actions.
- John did what he had to do. The people who became collateral damage, or who loved the people who became collateral damage, are going to make sure he won't live to be part of those who reap the benefits.
- Played For Horror:
- The atrocities shown by the plot, both the ones performed by John and the ones that would come to happen if John did not "do what he had to do", are equally mind-boggingly awful. The fact John is supposed to be the lesser evil is deliberately presented as not a reassuring thought.
- John very quickly decides that anybody who doesn't agrees that he is doing what needs to be done must be eliminated as a potential enemy or obstacle, and the body count takes off like a rocket.
- John decides to commit suicide as penance for doing the atrocity that had to be done. It only serves to make the rest of the cast more mentally unstable.
- John did what had to be done. A reassuring thought, he thinks. Pity about that kid he traumatized with what had to be done that will grow up to become a Serial Killer and hunt him down. John will die, slowly and painfully, with that phrase on his lips.
