For me it has to be Star Trek TOS “The Conscience of the King”
McCoy is talking to Kirk about the suspected mass-murderer in hiding as Karidian. He accosts Kirk and says, “What if you decide he is Kodos? What then? Do you play God, carry his head through the corridors in triumph? That won’t bring back the dead, Jim.”
So now Kirk as the hero realizes that vigilanteism is wrong and takes the right path and bring him to legal due-process right?
Fuck that!
“No, but they may rest easier.”
I imagine Kirk punching some Spaceman Second-Class in the nuts and banging Yeoman Rand and her sister on his way to the next scene
Off the top of my head, without giving it a ton of thought “The greatest trick the devil ever pulled was convincing the world he didn’t exist.” Verbal Kint - The Usual Suspects
Citizen Kane. Jedediah (Joseph Cotton) has written a scathingly unflattering (but completely accurate) review of his boss C.F. Kane’s wife’s operatic debut. When Kane himself shows up, Jedediah asks if they are on speaking terms.
“Who am I? I am Susan Ivanova. Commander. Daughter of Andrei and Sofia Ivanov. I am the right hand of vengeance and the boot that is going to kick your sorry ass all the way back to Earth, sweetheart. I am death incarnate, and the last living thing that you are ever going to see. God sent me.”