It depends what you mean by evil really.
Some people are born with brain disorders such as psychopathy or sociopathy. Many people have these conditions without ever committing a crime in their whole lives, others may go on to become serial murderers or con artists etc.
Clearly some are born with defects of the brain that can cause them to do some very rotten things, some people just have a capacity to do things with little regard for others.
Categorization into 'good' and 'evil' pigeonholes are a human construct/activity so I don't think we can reasonable ask whether such an unnatural definition is with us at birth.
We get a set on neurons that will tend to connect according to that which we started with from the information from our parents, and that which we experience after birth also. So both nature & nurture forms personality, although it's unclear the ratio range.
To add, I was working in a local Hospital with persons with L.D. one person said to me, his G.F. Bought him a knife because she did not like this other girl & asked him to knife her, he did, to death!
As some people are born to be leaders, innovators and some will always be followers or the stalwarts behind the scenes I think some are born with more of a propensity than others to be evil and some are just evil. Definitely nurture also plays a part in a lot of cases especially in cases of delinquency that matures into just a life of petty crime and the like but some are born just evil and do horrendous things that nurturing would not have altered.
We're born with a clean slate. It's upbringing that shapes how we'll be as adults. A warm loving home will likely produce children who grow up to be decent people. A chaotic upbringing probably sows the seeds of chaos and misery in the lives of the children who endure it.