Charlie Zelenoff is probably the worst. He became infamous for going around and challenging random people to fight. If they accepted, he would usually sucker-punch them immediately. He also challenged professional fighters and pissed some of them off so much that they beat his ass. He would edit the videos to make it seem like he won, or at least didn't lose. After Charlie became famous, there was a Youtuber who gave him a taste of his own medicine and beat him in a street fight. Charlie then changed his style of content and began filming himself sucker-punching random people on the streets at night.
If I remember correctly, he's now facing something like 9 years behind bars.
https://youtube.com/watch?v=ux_kUo9OLsc
https://youtube.com/watch?v=DeH-iGw-6xQ