She told a line judge, "I'd take this ball and shove it down your f***ing throat" at the 2009 US Open.

Julian Finney/Getty Images

Source: Daily Mail

She destroyed a racquet at the 2013 Australian Open.

Source: Buzzfeed

She allegedly unfollowed 20-year-old Sloane Stephens on Twitter after she beat her at the Aussie Open.

ESPN2

Source: SI

She also refuses to be Stephens' mentor.

Mike Ehrmann/Getty Images

Source: SI

She played the 2013 Australian Open on a grotesquely swollen ankle.

@SerenaWilliams

She flipped out on a US Open official and called her a "hater" after she penalized her for grunting.

Watch the tantrum here >

She doesn't think she has any legitimate threats.

ESPN

Source: Arcamax

She refuses to play at Indian Wells (one of the most popular events on tour), because fans booed her sister there in 2001.

Adam Pretty/Getty Images

Source: NY Times

Even though she had won 19 matches in a row, she wrecked a racquet when she lost to Angelique Kerber last summer.

(via Bleacher Report)

She has destroyed her sister when it matters. She's 8-3 against Venus in finals.

REUTERS/Kevin Lamarque

She had an emotional breakdown and started crying at the 2012 French Open, when it looked like her game might never recover.

Tennis Channel

Watch the full video here >

She reportedly holds a grudge against Justine Henin because she called a timeout in the middle of Serena's serve 10 years ago.

Alex Livesey/Getty Images

Source: ESPN

She could have retired after a life-threatening pulmonary embolism in 2011, but she fought her way back.

Vince Caligiuri/Getty Images

Source: ESPN

When wild fashion became a thing in women's tennis, Serena out-did them all.

Al Bello/Getty Images

She has been a 24/7 tennis player since she was a toddler. Her sister said of her regimen:

YouTube

Source: NY Times

Serena Williams is one of our Most Impressive People of the Year.

Mike Nudelman/Business Insider

Check out the 20 Most Impressive People of the Year »