ISTANBUL — The way the season has gone for Serena Williams, there was only one fitting way for it to end.
Williams capped a career year in style Sunday, earning her 11th title by coming from behind to beat Li Na 2-6, 6-3, 6-0 for her second straight WTA Championships crown.
Williams became the eighth woman to win 11 or more titles in a year and the first since Martina Hingis had 12 in 1997. The American also is the first to repeat as champion at the season-ending WTA Championships since Justine Henin in 2007.
"It was an awesome year of tennis," said Williams, who sank to her knees after firing a backhand winner on her second match point.
The victory brought Williams' prize money total for the year to $12,385,572. The only player, male or female, to earn more in a year was Novak Djokovic with $12,803,737 in 2012 and $12,619,803 in 2011.
Williams won the event for the fourth time, having captured the elite tournament for the top eight players also in her debut in 2001 and in 2009 and 2012.
Williams has won 78 of 82 matches this year and will finish the year as the top-ranked player for the third time in her career after 2002 and 2009. Williams' titles this year included the French and U.S. Opens for a total of 17 Grand Slam crowns. Her winning percentage of .951 is the best on the tour since 1990. Martina Navratilova had an 86-1 record and a .989 percentage in 1983.
Still, Williams said she would have preferred to have won at least one more Grand Slam title.
"I live to win slams. I mean, obviously I'm so excited to be the WTA champion," Williams said. "I can't say it's the best (season). I can't say it's not the best. I don't know. I really don't know."
At Basel, Switzerland, Juan Martin del Potro denied Roger Federer his hometown Swiss Indoors title for the second straight year, winning the final 7-6 (3), 2-6, 6-4.
The top-seeded Argentine clinched the title when Federer could not return a forcing forehand.
"It's always a pleasure playing against you," del Potro told Federer during the trophy ceremony. "I know you are the hero here and for me a big inspiration, too."
Federer had hoped the raucous support at Basel, where he is a five-time champion, could help revive his difficult season. He's won just one title in the past 14 months.