#6. AJ Styles

AJ Styles was never expected to reach the levels that he did in WWE. When he was signed in 2016, The Phenomenal One himself admitted that he only expected to be a midcard Superstar, intending to make good money before retiring in a few years.
However, when talent is that good, it's impossible to deny them. Vince McMahon only realized months after signing AJ Styles that he ended up acquiring the best in-ring performer of this generation.
Look who just shut down all of Tony Khan's critics! More HERE.
It took Styles just over two months to get into the World Championship picture and PPV main events and while he wasn't successful in his first couple of attempts against Roman Reigns, he ended up capturing it from Dean Ambrose just over seven months from his WWE debut.
That was the first of two Championship reigns - the second of which lasted a full calendar year - putting him in an elite crowd such as Bruno Sammartino, Hulk Hogan, John Cena, Pedro Morales, etc.
While it's not known how many more years Styles has left in him, he's undoubtedly closer to retirement than most of the WWE roster. He may never get released as WWE knows that they have to utilize him as much as they can while they have him.