Michael Phelps went viral for his death-stare at Chad le Clos at the 2016 Rio Olympics, as he sought to avenge his 200-meter butterfly loss from the previous edition. However, the American swimmer went on to clarify later that it wasn't intentional.
Phelps and le Clos faced in the 200m butterfly finals at the London Olympics, and despite the American swimmer being at his best, he lost to the South African and finished outside of the podium. The pair met again in the 200m butterfly semifinals at the Rio Olympics, and Phelps was captured seemingly giving a death stare to the rival swimmer before the race.
After Phelps beat le Clos in the final and reclaimed the gold medal, his face went viral overnight. However, he clarified following the Olympics that he didn't intend to give a dirty look to the swimmer and was just in his zone at the time.
“I just had music going on in my head. I had thoughts going on in my head, spitting water a little bit all over the place, so I was in my own zone,” the 28-time Olympic medalist told TODAY in August 2016. “I was not intentionally mean mugging him or giving him a dirty look.”
In addition to the 200m butterfly title, Phelps won gold medals in the 200m medley, 4x100m freestyle, 4x100m medley, 4x200 m freestyle and a silver in the 100m butterfly. With 23 gold medals to his name, the American swimmer retired as the most decorated Olympian in history following the Rio Olympics.
"I didn't want to end my career like that" - Michael Phelps on why he came out of retirement for the 2016 Rio Olympics

Michael Phelps initially announced his retirement following the 2012 London Olympics, and while he had won four golds and two silver medals, the American swimmer claimed to have lost his love for the sport. He didn't want to retire like that, thereby coming out of retirement for the Rio Olympics.
“I wanted nothing to do with the sport then and that's why I came back. I didn't want to end my career like that. I had to find the passion myself again. And I found that again and I had fun. And this is how I wanted to finish," Michael Phelps explained in the above-mentioned interview.
Phelps had been dealing with depression around the London Olympics, and it became so severe following his retirement that he had been contemplating suicide. He battled through mental health issues in the years leading up to the Rio Olympics, eventually regaining his love for the sport to sign off his all-time great career with five gold medals.