Are we talking about childhood bullying?
Its often said that bullies are often bullied themselves (at home or elsewhere) I think that's a load of botox. Some people...right from childhood...are born selfish, egotistical, morons who will trample on anyone to assert themselves without any thought for the harm they cause. Ive seen it (and was a victim of it) in school. But it carries on unchecked through life. Seen it in school, the home, prison, the workplace, family life etc. Not sure what the answer is.