How can I stop him from being a bully?

Hello! I am an 18-year old public highschool student boy.

How can I stop my 17-year old brother (who is skilled in Wrestling, BJJ, Muay-Thai, & Boxing) from being a bully? He's a unique bully in that he only targets other bullies.

For example, he brutally beat up and humiliated a teen skater who bullied a deaf boy.

Also, my 17-year old brother also brutally beat up a college frat boy after gaining info about the college frat boy pulling cruel pranks on a midget special needs kid.

My 17-year old brother was so brutal towards his victims to the point that many bullies stop acting like bullies in front of him or just avoid him.

Also, my 17-year old brother is crazy. He doesn't get scared if bullies are strong, aggressive, sadistic, or have huge numbers. He said to me that he always likes a challenge.

It seems like he's literally the opposite of the stereotypical bully (the types who pick on lone meek weaklings) because the stronger, the more sadistic, the more aggressive, the more evil, and the more powerful his targets are, the more he wants to fight them.

My 17-year old brother is also arrogant in that when an adult told him that he's a good person for fighting bullies, my 17-year old brother just laughed at the adult and told the adult that "he's just a bad person destroying other bad persons'.

I think my 17-year old brother is crazy. One day, he will die because he is so reckless.

How can I stop my brother from being a bully?
How can I stop him from being a bully?
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