in my opinion it's a combination.
and I give 30% to nature and 70% to nurture.
I do not like when everything is explained by DNA and genes. Because even if you got some shit in your genes, you still need activation of that shit, to make that shit happen. The environment, and upbringing can be a push for that activation. But I am sure, that even when you got inclination for some evil/bad stuff, you still can resist it and use your head.
Sometimes even crimes and all the qualities of the character are explained with genes. I bet that you've seen articles with title like that "Scientists found out that
it is a special gen for stealing" or "...for adultery" or whatever else like that. I do not accept that way. Ok, I do not argue that they can find some gen, but it is just like windows register: you can right click at the screen, and change some options in common properties window, and it will be just like upbringing. but you can go deep in the DNA, using some registry-tweakers, and change the same option "from inside", by adjusting some entry "534df65500ER6-666h-OOOT" parameter to "54647-435-fffd0". But you know that sometimes by editing options in this way careless you can crash the whole system. The same is with genetic engineering.