The 2018 U.S. Open ended with a dramatic tournament-altering game penalty against Williams. Naomi Osaka dominated the first set, breaking Williams twice to win, 6-2. Early in the second set, chair umpire Carlos Ramos issued a warning against Williams for coaching from the stands.
Williams immediately challenged Ramos, telling him, "I don't cheat to win. I'd rather lose." Williams was up a service break, but Osaka broke back to get back on serve at 2-3.
Williams then smashed her racket to the ground, and Ramos issued a point penalty for racket abuse. Osaka, starting up 15-0, served out the game at love to tie the set at 3-3.
After breaking Williams again with a brilliant passing shot to her backhand side, Osaka was up 4-3.
As the players switched sides, Williams went off on Ramos. "How dare you insinuate that I was cheating? You stole a point from me," she said. "You're a thief, too."
At that point, Ramos issued a verbal abuse warning and awarded a game penalty to Osaka, giving her a 5-3 lead.
Williams called for the referee and, in tears, complained that, "There's been a lot of men out here that have said a lot of things ... 'cause I'm a woman you're gonna take that away from me?"
Serena won the ensuing game on her serve, but Osaka held to take the championship.
Williams met Osaka at the net with a gracious hug, but then turned to Ramos and pointedly said, "You owe me an apology."
At the trophy ceremony, the crowd booed until Serena put her arm around a tearful Osaka. "She played well and this is her first Grand Slam ... let's make this the best moment we can. Let's not boo anymore ... Congratulations, Naomi."
After Osaka was presented the trophy, she quietly said, "I know that everyone was cheering for her and I'm sorry it had to end like this ... I just want to say thank you for watching the match. It was always my dream to play Serena in the U.S. Open finals. I was really grateful to be able to play with you. Thank you."