I am convinced that the vast majority of violence in the world is caused by bad parenting. Yes, a very small minority of people are naturally evil, but we can put systems in place to deal with them effectively. Most people, however, are evil because how they were raised. No one saw the warning signs at an early stage and dealt with them. And the reason for that is because well over 99% of all parents have no clue what they're doing. They never learned to develop the proper faculties, so they fall back on the same devious tricks their parents used to raise them, and the great circle of crap makes another turn.
What is violence? Violence isn't just hitting. In fact, violence mostly has no physical component at all. Most violence is psychological. Lying, bribing, using guilt or shame or envy to manipulate, hypocrisy, threatening, all forms of deception and mind games are forms of violence.
Why do people lie? Because their parents lied to them so they think lying is acceptable. People see all the horrible things their parents do to them as children, and it forms a mental program. If parents can do it to children, which should be the closest bond, and that's okay, then there should be no problem doing it to a stranger. It is a self-perpetuating system.
Children are a parent's number one priority. Children are a parent's number two priority. Children are a parent's number one hundred priority. Everything else is dust in the wind. You made the mess, you opened the door and brought someone into this world - without consent - who will suffer, grow old, and die. You did that, now it is your responsibility to fix it. You created this disaster of human suffering, now it is your responsibility to alleviate it.
Similarly, the solution to violence in the world is good parenting. That too is a self-perpetuating system. The more good parents there are the more children will grow up to become good parents, and then the system will flip and violence will diminish.
There is no other solution.