Answer:
First and foremost, as what people would always say "Violence is never the answer", you have to convince first that person about his/her purpose of bullying. Second, find for a suitable solution that could settle his/her conflict towards that person and for what reason. Lastly, if they're too hot-headed let them calm down first and think deeply about the advice you gave them.
Explanation:
Apparently, I've done this sort of methods before. Hopefully it could help.
