The capacity for what we humans would deem as good and evil are in every one of us, imo.

Some of us are lucky enough to be born with an intrinsic sense of wanting to focus on the good - and it does pay dividend, that's how we evolved as a species.

Still others were treated badly themselves and so they are consumed with anger etc and they focus on their capacity for evil. Some of us, perhaps most of us on this forum, were treated badly and yet have the courage to believe in something better for ourselves.

Many people have limited ability to reason and act purely from brain driven instincts for survival - and psychological threat can lead a person to do some pretty horrific things.