Adam Cole
The NXT Champion and leader of the Undisputed Era had to be on this list at some point right? With Finn making his return to NXT to square off against Cole it is surely only a matter of time before Balor is standing across the ring from Cole in a Championship match.
NXT does have less of an issue when it comes to a heel/heel feud. The 'main roster' of WWE would rarely have a defined heel take on another, as the crowd would have difficultly deciding who to cheer for and the match would lack an atmosphere.
In NXT however you would not have that issue. The Undisputed Era undoubtably have their fans and Balor himself received some positive reaction when he attacked Gargano and raised the fingers in a gun pose.
A top AEW star just called one of his colleagues 'spoiled' and 'narcissistic' HERE.
There's also a chance that by having Cole and Balor feud the OC may be able to make some sporadic appearances on NXT. Given the history between Balor, Gallows and Anderson could you imagine if this all lead to a War Games match between The Club and The Undisputed Era?