Where do you draw the line between a mistake and a purely evil act? i don't think they put on the earth to be evil, when you look back at their life, usually they were the one treated badly in the beginning, either at school or by their parents.
honestly, if i were in somebody else's shoes, i have no idea who i would be or how i would deal with what has happened to me. i could have been hitler in another life, i have no idea.
so no, i do not believe any one person on this earth is completely evil. there so many emotions to every being it is inconceivable. i think fear is a more popular emotion, rather than evil, especially in children/teens.