Busta Rhymes did much more than just throw a protein shake during that fight in a gym -- surveillance video now shows him totally losing it on an employee!
The incident went down in August at Steel Gym in NYC ... and the video, first posted by Page Six, shows Busta in some kind of verbal dispute with the employee who's sitting behind the front desk.
At some point the rapper gets tired of talking and throws a liquid at the man, then clears the counter top ... taking out everything in front of the guy ... including his computer monitor.
As we reported, Busta struck a deal with prosecutors. He'd been arrested for assault, but ended up pleading guilty to 2nd degree harassment. He avoided jail time and agreed to anger management classes.