6. Kurt Angle
In 2003, doctors told WWE Champion Kurt Angle that he should retire from pro wrestling; at that stage, most normal people would have listened to that advice. After all, Angle could not feel his arms and was suffering with a broken neck (having already had a broken neck as an Olympian). At the time, he was the best pro wrestler in the world, and as a multi-time WWE Champion and pay per view draw in the hottest era of pro wrestling, he would have been able to retire with a fantastic legacy despite a relatively small career. As an Olympic gold medal winner in real wrestling, Angle had already hit his lifetime defining moment - there was no need to keep doing pro wrestling. But such is the size of Kurt Angle's ego, he couldn't bring himself to retire, despite knowing the end result could see him in a wheelchair. He was convinced he was invincible, and thought normal rules of physical limitations would not apply to his body. Angle would go on to continue with WWE through further neck surgeries and pain killer addiction, despite the fact that continuing was literally killing him. But the ego wouldn't let him stop: he wanted to continue in order to be considered the best pro wrestler of all time, driven both by his natural competitive drive, and also a fool-hardy conviction. It got to the point that WWE had to cut Angle loose from the company, as people within the business became convinced that Angle would be the next Benoit or Guerrero. That should have been a wake up call to Angle, but rather than taking stock of his life and physical limits, he instead signed with TNA. He has had mixed success since; there's no doubt he can still be the best talent in the world at times, but his recent career has been blighted by drinking incidents and rehab stints as he looks to prolong a wrestling career that should have ended ten years ago. The man's legacy is complete. He should return to WWE for one last goodbye match and then retire with a WWE Hall of fame spot, as one of the best ever, but who is long overdue retirement.