#4 Feud with Seth Rollins for the WWE Universal Championship

While Brock Lesnar is now WWE Universal Champion, it's plausible to believe that Seth Rollins will regain the WWE Universal Championship at WWE SummerSlam. The most obvious WWE Superstar to come after his championship would be Finn Balor. Sure, it's possible that AJ Styles could be the guy but it's already been done.
Establishing Finn Balor as a heel Universal Champion has more rewards than Brock Lesnar. Making sure that Seth Rollins remains in the chase adds more to the story. Some WWE Superstars are better chasing the title rather than having it. Seth Rollins deserves that sort of a run, which he didn't really get when he went after Brock Lesnar.
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It's a win-win situation as it sets the stage for the true main event of the story. Like all stables that have come before it, something has to give.