Brock Lesnar was the first big name in the WWE to make the transition into the UFC. It proved to be a successful one, to say the least, when he managed to win the world heavyweight title after just three fights with the company.
His MMA career was hampered by a bout with diverticulitis in 2009, after his maiden title defense and rematch against fellow former champion Frank Mir. After being sidelined for a year, he returned in July 2010 to defeat then-interim champion Shane Carwin.
Lesnar dropped the title to Cain Velasquez three months later, and was never the same again when he faced Alistair Overeem more than a year later, after being struck with a second case of diverticulitis.