What happens if a martial artist bullies others?

My uncle told me the story about a HS bully no one dare to stand up to nor fight back.

That guy was just 5'9 but he strong and advanced in Krav Maga and had a black belt in BJJ. He used his skills to bully others. Everyone and my uncle were afraid of him.
Update: What happens in that case? If a martial artist uses his skills to intimidate others for no reason other than for power and control and enjoys it?
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