#3. Shelton Benjamin
Shelton Benjamin was originally supposed to return shortly after the brand split returned in 2016. In fact, WWE had even teased his return with a promo. However, due to medical issues, he still had to undergo surgery and deal with all sorts of issues and as a result, he didn't sign his WWE contract.
The door was, however, open to Benjamin and he took it in 2017, returning and teaming with Chad Gable. The problem was that once Gable was moved over to RAW, there was nothing for Benjamin to do.
Now, we understand that his role in the first place was generally to help put over younger superstars and be at a midcard level. But the way Benjamin has been on the sidelines is almost injustice.
The fact of the matter is that Benjamin is still a top-level performer and can put on great matches. The only way for him to do that, it seems, is to leave WWE and he's probably counting the days till he can.