#2 Brock Lesnar
If Reigns should be considered a candidate, then it also stands to reason that his opponent, and current Universal champion, Brock Lesnar should be considered as well.
If Lesnar loses his title at the show, and given the circumstances that is a real possibility, then he will be out for revenge, and seeing him arrive as the 50th entrant into the match and destroy everything in his path would no doubt be a thing of beauty.
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Like Cena, Lesnar is a household name, and if the company are serious about wanting to break this market, which it certainly looks like they are, then having Lesnar win would certainly help them do that.
Lesnar pulling double duty seems highly unlikely, but if he does enter this match, then he has to be considered a favourite to win.