She told a line judge, "I'd take this ball and shove it down your f***ing throat" at the 2009 US Open.
Source: Daily Mail
She allegedly unfollowed 20-year-old Sloane Stephens on Twitter after she beat her at the Aussie Open.
Source: SI
She flipped out on a US Open official and called her a "hater" after she penalized her for grunting.
She refuses to play at Indian Wells (one of the most popular events on tour), because fans booed her sister there in 2001.
Source: NY Times
Even though she had won 19 matches in a row, she wrecked a racquet when she lost to Angelique Kerber in 2012.
She had an emotional breakdown and started crying at the 2012 French Open, when it looked like her game might never recover.
She reportedly holds a grudge against Justine Henin because she called a timeout in the middle of Serena's serve 10 years ago.
Source: ESPN
She could have retired after a life-threatening pulmonary embolism in 2011, but she fought her way back.
Source: ESPN
She has been a 24/7 tennis player since she was a toddler. Her sister said of her regimen:
Source: NY Times