5- Edge
A neck injury was the reason Edge had to retire from this business so early. Edge is still one of the most courageous wrestlers in the business, taking many bumps throughout his career in TLC matches in the tag team division and has been involved in risky situations as a singles star. Although he had a scheduled match against Alberto Del Rio for the World Heavyweight Championship at WrestleMania 27, Edge was also getting multiple tests read on his neck issues.
Edge still defended his crown, but a week later on Raw, he made the announcement no one wanted to hear. There was too much damage to his neck. Not only was it career threatening, but life threatening. He immediately retired from the company.