It's hard to say because she has won so many titles in her career.
In singles, she has won the Australian Open five times, Wimbledon four times, the US Open three times and the French Open once. That's a total of 13 Grand Slam singles titles.
Add to that, 12 more Grand Slam Doubles titles and two more Grand Slam Mixed Doubles titles for a career total of 27 Grand Slam titles!
She has also won two Olympic Gold medals in doubles in the Summer Olympics (2000, 2008).
With a career that impressive, it's hard to pick one thing out and say that's her biggest accomplishment.
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sarena willams known 4 tennis. . .. . . .. The world best tennis player. . . . . 2DAY willams celebrates b'DAY that is 26 sept 1981. . .. any way hats of to willams. . . .
Well she is opening up a school and making a new lip balm and she won a grand slam award.