#1 CM Punk

Every Superstar mentioned in this article returned to WWE after their initial departure, except for CM Punk, who is yet to show up on WWE TV since his release in 2014. In 2011, everyone knew that Punk was going to leave after his contract expired that year, and it was even acknowledged by WWE themselves.
What fans didn't see coming, however, was his departure from the company in 2014. Punk reportedly had heat with Triple H backstage, and his mistreatment in the company as well as being denied an opportunity to main event WrestleMania all played a role in his exit.
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After his release, he publicly spoke about his experiences in the company in podcasts and interviews including his medical issues which he accused WWE's doctors of mistreating. This resulted in a legal battle between him and the company.
The Straight Edge Superstar retired from pro wrestling and vowed to never return. His exit was very surprising and unexpected since he was a big star and a former WWE Champion. CM Punk surprised fans yet again when he joined the FOX produced show WWE Backstage in late 2019.
Although he worked alongside current WWE Superstars on the program dedicated to WWE, he is yet to make an official return to pro wrestling.