#1 Bobby Lashley
This may be unlikely, as Lashley seems poised to go deep into the Raw main event picture after being booked very strongly. However, that doesn't mean that WWE puts him through a re-acclimatizing phase in which he is made to work a little below the main event, just waiting in standby to be part of the next marquee feud.
A rivalry with Rollins over the Intercontinental title is just one big thing. M-O-N-E-Y. Lashley is a monster who has come back after honing his craft on the independents and would be perfect to fight Rollins.
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Lashley is a powerful and dominating brute, whereas Rollins is a crafty aerialist that has grounded men like Brock Lesnar with his offense. That would be a phenomenal dynamic to play with.
There is no right or wrong answer to who wins this feud, as holding the secondary championship isn't really a demotion anymore.
Both men can hold this belt and keep themselves looking strong and not hurt the prestige of this belt. Both can lose and move up or down the card without a hitch. This really would be one of the perfect feuds to come out in the post-WrestleMania WWE landscape.