You don't just have people who wake up in the morning and say, "What evil things can I do today, because I'm Mr. Evil?" People do things for what they think are justified reasons. Everybody is the hero of their own story, and you have to keep that in mind. If you read a lot of history, as I do, even the worst and most monstrous people thought they were the good guys. We're all very tangled knots.
In the US. Infantry Manual published during World War II, the soldier was told what to do if a live grenade fell into the trench where he and others were sitting: to wrap himself around the grenade so as to at least save the others. (If no one "volunteered," all would be killed, and there were only a few seconds to decide who would be the hero.
I wish heroes didn't exist. Whenever we need a hero, it's because there's a problem that needs to be solved; it's because two groups of people, or two countries, are hurting one another, so a hero is needed to save us. If everyone were at peace, if everyone were happy, why would we need heroes? The world is better off without heroes.