#4 Neville

The man formally known as Adrian Neville on NXT (and as Pac down on the indies) belongs to a very rare group of Superstars whose popularity on the main roster has probably surpassed the level he enjoyed on NXT.
Usually, a Superstar who has the full backing of the WWE Universe will ascend up the ranks to RAW or Smackdown and see their stock plummet due to bad booking. It's refreshing to have seen somebody go in the opposite direction.
Did you know a top WWE Superstar just wrestled outside the company? More details HERE
While still a fairly popular NXT Champion, Neville was around during a boom period that saw him compete against the likes of Sami Zayn, Kevin Owens, Finn Balor and Hideo Itami. All of these men were arguably more interesting to fans than the semi-vanilla babyface, Neville.
Initially, his time on the main roster looked to be going the same way. People were highly impressed with his athleticism but couldn't fully connect with him as a character. That all changed when he was turned heel and sent down to 205 Live.
By WWE's usual standards, this should really have been a demotion. The Cruiserweight Division wasn't exactly setting the world on fire following the conclusion of the Cruiserweight Classic, and the idea of a high flying sensation playing a heel didn't sound like it would work one bit.
Much to our surprise, Neville took what he had been given and actually became a very convincing heel, calling himself the 'King of the Cruiserweights'. Considering the Brit was the only person that casual fans didn't mind watching whenever the cruiserweights came to RAW, this was a pretty apt. nickname. Neville took a division from the brink of collapse to one that could legitimately showcase title matches on PPVs like Wrestlemania.
Neville is no longer with the company, of course, but his time representing the WWE Cruiserweights has opened doors for the man from Newcastle, and people should be excited about where he ends up next.