A foolish demand. First off, define “evil.” One person’s atrocity can be another person’s good time. Second, what if you’re mistaken? What if you find a pedophile luring a kid into his van and kill him, and then discover he was actually the child’s father picking them up from school? You can’t just bring him back to life if it turns out to be a bad idea. Hell, even if the person does fit your definition of “evil,” it can be a bad idea. Saddam Hussein was a bastard in most people’s eyes, but look what happened when he got taken down.
As with many things in life, there are Discworld quotes that illustrate the problem:
“Shoot the dictator and prevent the war? But the dictator is merely the tip of the whole festering boil of social pus from which dictators emerge; shoot one, and there’ll be another one along in a minute. Shoot him too? Why not shoot everyone and invade Poland? In fifty years’, thirty years’, ten years’ time the world will be very nearly back on its old course. History always has a great weight of inertia.”
“You had to deal every day with people who were foolish and lazy and untruthful and downright unpleasant, and you could certainly end up thinking that the world would be considerably improved if you gave them a slap. But you didn't because, as Miss Tick had once explained:
a) it would make the world a better place for only a very short time;
b) it would then make the world a slightly worse place; and
c) you're not supposed to be as stupid as they are.”
You are not John Matrix, and you are not living in an action movie. You can’t solve the world’s problems by killing everyone you don’t like.