Serena Williams received three code violations in the US Open finals against Naomi Osaka. The first was for receiving coaching from the stands and the second was for demolishing her racquet out of frustration.
The second code violation — which occurred a bit after the first; the racquet smash was at the end of a lost game — led to a lost point, and Serena went up to the chair umpire and berated him, insisting that she didn’t receive coaching and that she has a daughter and wouldn’t cheat. She lost the game in which she’d been docked the point, and then continued berating the umpire, loudly calling him a thief, and was eventually docked a game in addition to the point she’d already lost.
What initially triggered Serena was when she was warned after receiving a gesture from her coach (which she has insisted was not coaching; the umpire thought the coach was instructing her to go to the net, Serena said it was a thumbs up):
The game penalty was pretty astonishing — yes, Serena was berating the umpire, but you want to see these things decided on the court. After the match, Serena’s coach did say that, yes, he was coaching but that this is something that everyone does and goes uncalled.