How to understand violence and addiction, nature or nurture?

Is there any real basis for there being a genetic predisposition towards aberrant behavior? Can criminality be understood outside the context of of environment? I have heard that violent criminals inside prisons are more likely to have a genetic or chromosomal disorder that makes them more likely to be violent criminals. But these same criminals almost all have something horrible (abuse,molestation,and so on) in their backgrounds too. I have also heard that plenty of people have these genetic violence markers, but don't become violent if they were raised in a normal, healthy environment. Of course plenty of people come from horrible and abusive backgrounds and grow to be normal healthy adults. What about addiction? Everyone that has a glass of wine doesn't become an alcoholic, but some do. Children of addicts are more likely to be addicts themselves, but is that genes or environment?