#1. CM Punk - Left WWE in 2014
It's hard to imagine that seven-and-a-half years have passed since CM Punk's departure from WWE and wrestling in general. It's almost as long as his entire WWE tenure, and after quite a few years, fans finally seem to be disinterested in his return.
With that said, Punk never teased a return to WWE. His biggest source of frustration was the hectic schedules, rough injuries, and creative limitations. The latter particularly had a great impact on his decision to walk away from WWE.
CM Punk was expected to return to WWE at some point, and there have been instances where the company has been open to negotiations. The closest he came to a WWE return was when he was signed to be a part of WWE Backstage on FOX. That was ultimately canceled, and he has been vocal about his criticism of his former employer.
Interestingly, a lot of the rift that he had seem to be with Triple H more than Vince McMahon. But at this point, the door is likely closed on a return to WWE, and fans don't care as much as they did a few years ago.