Unfortunately, there is no definitive answer to this question but I will do my best to unpack what contributes to people showing anti-social tendencies. There has always been the nature – nurture debate. Are you a product of your genetics (nature) or are you a product of your environment (nurture)? The current thinking is that we are all a product of a combination of the two. Some experts believe that genetics create the ‘ceiling’ (our personal limits) and the environment suppresses or helps us to express our genetic strengths and weaknesses.
For example – a psychopath will have a genetic predisposition to become an evil person but the environment in which they grow up in will determine how their genetics play out. The general rule is that if a psychopath grows up in a loving stable home, they will be less likely to develop into a psychopath. If they grow up in a troubled abusive environment, that environment will encourage and nurture evil behaviour. Of course there will always be exceptions to the rule.
If you have seen to Oscar winning film “Joker” starring Joaquin Phoenix, this movie shows the development of psychopathy. A difficult childhood and then adverse experiences growing up and as an adult. The more a child is treated badly, the more they leanr that the world is a bad place that doesn’t support them. Some children will become more passive and some will become more aggressive to protect themselves.
Evil doesn’t exist in a vaccuum, and whenever I have worked with troubled individuals it is common to be able to trace the reason for their difficult behaviour. Often they have felt misunderstood and undervalued. It is less common for those from happy, stable and loving backgrounds to end up voluntariy wanting to hurt or harm others.