The ice man was interesting with how he had in him a genetic trait that could have easily made him into a heroic character. He had this risk-taking adrenaline craving mentality which could have made him into a fireman or a police officer, but unfortunately turned him into the opposite. Heroes and villains are in no doubt opposites, but have the same traits when it comes to taking risks and being attracted to an adrenaline rush.
It's very interesting material - things like the similarities between good and evil, genius and insanity.

The way I look at it and probably people in general, we are all products of our environment. Evil lives is in us all just like cancer. Something in your life triggers it. You may smoke all your life and never get cancer - not highly possible and also not smoke a cigarette your whole life and still get it. So you can have a serial killer with a great child hood and still have a possibility of snapping.

A comedian mentioned this, and I think it was Larry David, in his stand up about religion and how you get people that are good all their lives, follow the rules, read a Holy Bible everyday, and then go out on top of building and start sniping people randomly. I think he would be referring to that Texas shooter back in the 60s.

So a bad childhood, statistically, increases the chances of a child to become a serial killer, but doesn't guarantee as does with a good childhood.