#1 Lars Sullivan

Lars Sullivan made his NXT debut back in 2017 and has been billed as a one-man wrecking force ever since. While he's still got a lot to prove in WWE, his career has been marred by controversies already.
Sullivan had a number of high profile matches on the Black and Gold brand, but his only notable feud came against Kassius Ohno. He was supposed to become a part of RAW in January 2019 and vignettes of his arrival had already started to air by then. However, an anxiety attack prevented this from happening.
Did you know a top WWE Superstar just wrestled outside the company? More details HERE
Lars Sullivan eventually debut on the RAW after WrestleMania 35 and took out Kurt Angle in the process. His only proper feud on the Red brand to date has come against Lucha House Party. He would suffer a knee injury against the trio on a RAW episode in June and has been out of action since.
In the meantime, Sullivan has already been fined $100,000 by WWE for a slew of insensitive posts that he had posted on the Bodybuilding.com forum between 2007 and 2013. As of this writing, there is still no update about his WWE return.