Created very toxic atmosphere in a workplace. It's like he want people to be feared of him. Arrogant, thinks he's a Chinese elite. There were not only rumors but the actual cases of him hitting his workers, one of which was the head of engineering, Cong Li.
Firing people for no obvious reasons, yelling, throwing things, it's all him. Basically, he acts like a spoiled kid, but in fact it's a typical behavior for those who made it too fast. He was born in poor family and now he's a multi-millionaire. Typical rags to riches.
Once he threatened to track down and kill a person (and their entire family) who asked a question about if Tron currency dropping down to zero.
Made it mandatory his American employees use Chinese spy software to track their every step. The list of noncompliant employees was made and sent directly to him.
Paid reddit moderator to erase negative posts about Tron. When moderator threatened to make the payments public, he vanished shortly after, his account was deleted and he never been heard since then.
Justin Sun was taken to court by his former employees for labor violations.
His app store Tron Network where Tron has a piece of apps' revenue is full of scam apps, people at Tron know about that but prefer to do nothing.
There was a faked pre-recorded Tesla raffle which people noticed. There was a lot of shouting, wall kicking and door hitting after that.