Some people are simply inherently evil or mean. Sure environmental/experience factors certainly create alot of monsters, but some people are just born with it. I knew a kid like this once...was raised in a very kind, loving family, and the kids brother was extremely good natured and kind..but this little girl just took to physical violence before she was even 2 yrs old, over the childhood continued hitting, smashing, hurting people and seemed to genuinely relish it. Scary stuff.