Have I ever met anyone purely evil? Once--and keep in mind that is only my assessment as up to that point I could see the Divine Spark in everyone. As you say, we are a unique mix. However, most of us believe what we do is right or okay. We are all almost hardwired to this belief in ourselves. It is hard for anyone to do what they believe is wrong. They have to come up with a reason why it must be right.
That one young man...he wanted to do what was evil simply because it created more evil and that amused him. I still pray for him--haven't seen him in decades.