That's quite interesting (and horrible, obviously), but just to be clear I'm talking more about the people that had an active hand in things like the concentration camps rather than your local janitor snitch who perhaps didn't fully consider the consequences of his actions.
Thinking about it more, it's perhaps unfair or maybe misguided of me to suggest a serial killer. If you're a serial killer then you're most likely absolutely insane, your actions are likely something which you can't control, so are you as responsible as the Auschwitz guard that turns on the gas chambers? I don't know, but an interesting thing to consider.
Good thread idea, btw, I find stuff like this really interesting even if I'm no expert and likely wrong on all points