Lance Armstrong
Armstrong had one of the most inspiring stories ever because he recovered from cancer to become a seven-time Tour De France champion. The American star put cycling on the map and became a global icon. It was an incredible rise to fame because everybody knew who he was and admired his achievements.

However, it was too good to be true because of what happened next. He was a the forefront of one of the most notorious doping scandals ever. Armstrong was the ringleader of the devious scheme and he lost everything. In recent years he started a successful podcast but he was a persona non grata for a decade (via Reuters).