Mike Tyson
Tyson is probably the scariest boxer of all time because of his terrifying aura and devastating KO power. But the American superstar also had a lot of problems outside of the ring. He admitted he had a serious cocaine problem and even fought some matches while high. Tyson said that he used a prosthetic penis – the ‘Whizzer’ – to pass tests.

This also affected his relationships in real life because he became increasingly dysfunctional. He notoriously spent time in jail after a rape conviction. Many crazy incidents saw him lose the respect and love of fans. However, Tyson rebounded throughout the 2000s and now people don’t mention his dark past much (via Sportscasting).