#4 Timothy Thatcher
Since making his NXT debut earlier this year, Timothy Thatcher has already undergone a change in persona. By spurning tag team partner Matt Riddle, he essentially turned heel. That heel turn was solidified even further after his attacks on Riddle that led up to the Cage Fight between the two men.
After The Original Bro moved to SmackDown, Thatcher was given a layer to his character. In various weeks, we've seen vignettes of him teaching "students" his version of Catch Wrestling. Instead, he calls it "Thatch as thatch can."
He roughly shows pupils various submission moves while also reminding us that he's a mat extraordinaire. What's something that Lee hasn't really faced much in NXT? He's seldom battled performers that are mainly mat/submission technicians.
With Thatcher a vicious heel now, it makes sense that he'd try to attack the top dog in NXT. Since Lee is now precisely that, the new character trait could eventually lead to a showdown with Lee.
It might be for the North American Championship but Thatcher has shown in most of his matches that he's more than capable of having main-event level matches. We just need to revisit his battles with Riddle, Oney Lorcan, and the rest of his tag team matches for proof.
Lee will need all sorts of challenges now that he's the top star of the brand. They will come from every direction and one that's a technical savant would present the Limitless One with a new challenge. He's faced some men of similar size and those which have star power. Thatcher will provide all sorts of new challenges.