5. Conor McGregor
McGregor is unique because he is the UFC’s only true mainstream star. But he has threatened to leave the promotion hanging on multiple occasions. Once he refused to perform his media duties because he was training in Iceland. Then the UFC pulled him from the main event of UFC 200.
The Irishman also retired several times because he wanted to use his power against his employers. This has mixed results because the UFC doesn’t appreciate this. However, McGregor has more sway than any other fighter so he doesn’t suffer any severe consequences (via Independent).