Singapore - Serena Williams sealed her fifth WTA finals title on Sunday and took sweet revenge for her crushing loss to Simona Halep when she hammered the Romanian 6-3, 6-0.
The 18-time Grand Slam-winner was broken early in the match but she reeled off eight games in a row to humiliatingly "bagel" Halep, five days after the Romanian's 6-0, 6-2 win in group play.
The peerless Williams yet again proved she remains on top of women's tennis at the age of 33 after becoming the first player to win the season finale three times in a row since Monica Seles in 1992.
"She was playing so well and I was literally on the side of the court and I just laughed. I said, 'Serena, you have nothing to lose. Just relax!" Williams said.
"And then once I relaxed I just started playing better and kept making my shots."
Williams fired 26 winners to just five conceded as she sealed her fifth year-end title in a fourth different city, ending 2014 on a high as the world number one and US Open champion.
Alarm bells rang for Williams early on and she conceded the match's first break to go behind 1-2, to chants of "Si-mo-na" at Singapore's Indoor Stadium.
But the defending champion hit straight back, and aided by Halep's double faults she shrieked "Come on!" as she completed a sequence of three game wins in a row.
Halep's raking cross-court forehand got it back on serve but the frustrated Romanian pummelled her racquet on the floor as she was broken again to go 3-5 down, before Williams served out the set.
With Williams firmly in the groove, Halep's hopes of becoming the first player to beat the American in the same week were fast receding as it became an exercise in damage-limitation.
But a grimly determined Williams wasn't letting up and as she punished Halep's second serve and repeatedly rushed to the net, the second set raced past in just 25 minutes.
Williams brought up three match points on Halep's serve and after trying to cheekily drop-shot the first, she smashed home the second before celebrating with her arms aloft.
Williams, who withdrew from the China Open with a left knee injury, picks up the $2 047 000 winner's cheque along with the Billie Jean King trophy, which she also lifted in 2001, 2009, 2012 and 2013.
"I didn't expect this. I just started training because I had such a knee in Beijing so I wasn't even sure if I would be able to play here," she said.
"And now I've won the Billie Jean King trophy again so for me it's just really amazing, I'm so excited."
Fourth-ranked Halep had impressed in her wins against Bouchard, Williams and Agnieszka Radwanska as she became the first Romanian and the eighth debutante to reach the final.