#1 EC3

One Superstar who has been criminally underused in WWE is EC3, who was moved to the main roster in 2019 from NXT. It seemed like he would get pushed by WWE when he was in a feud with Dean Ambrose before his departure from WWE last year.
But, that did not happen. He fell down to WWE's Main Event show, but returned to prominence later in the year when he too was added to the 24/7 Championship picture. But, a nasty concussion has kept him out since November.
EC3 recently spoke about his injury in an interview with Fightful, stating that it was the toughest injury of his career:
"I will say that out of all the physical ailments I’ve had in my career—whether it was a torn bicep, torn ACLs, dislocated patella, herniated discs—coming back from this one was one of the hardest things I had to do."
In the same interview, he said that he feels "fantastic" and is seemingly fit and ready to go. With Paul Heyman offering several underused Superstars opportunities, perhaps EC3 could get a second chance after WrestleMania 36 on RAW.