#2 Lars Sullivan
Many great factions have a big man, an enforcer, a superstar that acts as the muscle. The Shield had Roman Reigns, Evolution had Batista and Undisputed Era couldn't ask for a better man to fill that role than Lars Sullivan. The man that many are deeming to be the next Brock Lesnar could make the Undisputed Era the most feared army in all of McMahon's empire.
While it is easy to see Sullivan laying waste to Cole, Fish, and O'Reilly for squandering his time with an invitation to join their club; clotheslines, running body presses, and his devastating waist lift side slam. The reason Sullivan could use Undisputed Era, however, is because those three moves are nearly half of his arsenal. Sullivan is as green as he can be, and while quick squash matches can hide his limited abilities to an extent, a spot in Undisputed Era would hide his weaknesses better than officials trying to hide him from McMahon (who is dying for him to develop asap so that he can be called up).
Lars Sullivan, the "Undisputed Monster" would be a force of nature that nobody in NXT or WWE could contain. This faction would be a launching pad for Sullivan's career to take off. Lars Sullivan is the next big thing, and so is the Undisputed Era.