#4. Adam Cole
Adam Cole has been a part of NXT for almost three years now. He's spent one-third of that time as NXT Champion, surpassing Finn Balor to become the longest-reigning NXT Champion in history.
While he's been an important figure to the Black and Gold brand, there's no denying that his time in NXT has gone on longer than it should have. One could argue that Adam Cole would have been ready for a main roster spot, but Triple H likely recognized that he wasn't needed at that point in time and utilized him in NXT instead.
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There's going to be a day when he moves to RAW or SmackDown and there's also going to be a day when he becomes a main-eventer. While a match with Brock Lesnar would certainly be amazing given their size difference (and the fact that Lesnar works better with smaller competitors), but it seems like the timing will ensure that their paths will never cross in the future.