A very fascinating documentary related to this topic is
Ice man Interviews . Netflix has the DVD.
Richard Kuklinski killed 100s of people in his life as hired hit-man. While serving several life sentences Kuklinski agreed to be interviewed on video by a Dr. Park Dietz because Kuklinski wanted to understand why he could kill people and feel nothing, either good nor bad. He knew he was a killing machine like no other, but didn't understand why. He didn't try to rationalize his behavior or justify it. Kuklinski was a very devoted family man who cherished his family above everything else, they knew nothing about his killings
After many hour of interviewing Kuklinski Dr. Park Dietz told Kuklinski that he was born with the same innate traits found in people such a fire fighters, they can face danger with little or no fear, and do extraordinary things that very few people can do. However in Kuklinski's case, he was raised by extremely abusive parents who beat him nearly every day of his life as a child. The combination of his innate qualities born to him (fearlessness) and the extreme abusive childhood, turned his fearlessness of danger into a powerful destructive force allowing him to kill and torture people without feeling any kind of emotions. Kuklinski could torture a screaming person for hours and Kuklinski would feel no emotions.
My thinking is that nobody is born evil, and deep deep down they never are, but I do believe that innate qualities born to any child, can be channeled into being used for good or for bad. A very stubborn child can grow up to real jerk and ruthless business person, or hopefully grow up to be a very determined and successful person using their natural talents for betterment of others as well as themselves.