#4 Triple H

HHH vs. Rousey is the most realistic option on this list given the history between the two superstars. The UFC Hall of Famer has been booked like an unstoppable force who never backs down from a fight, even if it's the legendary Game staring into her eyes.
The feud needs no build-up whatsoever as the backstory is enough to get the match going. The Game is now back as the on-screen authority figure which adds another dimension to the feud if the WWE decides to revisit it, strictly in terms of a one-on-one match.
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It's quite obvious that Triple H had a big role to play in Rousey's impressive debut performance at WrestleMania 34. They seem to have great chemistry too and just like his protege Orton, the Cerebral Assasin is an old vet who is adept at telling a compelling story inside the ring.