How do you define evil? I think it's different from just "mean" or someone who's a bully.
To me, "evil" means someone who pretends to be one thing, usually sweet and kind and nice and selfless, and the whole time they are hiding the fact that they are cruel, selfish, manipulative, and will do whatever it takes to make sure that not only do they win, but the people around them lose.
I also think they're absolutely very aware of their true self and they do whatever they can to try to hide it, oftentimes taking on the veneer of someone who's kind and generous and wonderful. The hard part is, we fall for this fake persona and it's usually hard to believe that the evil in this person is their true self.
They say that Ted Bundy, the serial killer, was extremely handsome and charming and kind and funny. To his victims, whom he charmed into getting in his car or coming home with him, it's likely they first time they saw the evil in him was when he was about the murder them. That's a reminder that just because someone is attractive doesn't mean we should assume they're as wonderful as their attractiveness says they are.
I grew up very innocently and never knew anyone I thought was evil until I was an adult. And it's funny, you don't really know they're evil until suddenly, without a doubt, they show you.
And it's shocking when it happens. You can't quite believe this person who had acted so nicely, is actually capable of doing what they just did.
I've experienced evil people a few times. Probably none of whom would murder anyone, but come to think of it, maybe they would if they were backed into a corner.
Check out this great article to see if someone in your life is evil.