#4 ...The main event of WrestleMania 36
The biggest (possibly the greatest) pay-per-view in WWE is WrestleMania. Every WWE Superstar wants to have his (or her) 'Mania moment.
Seth Rollins got his WrestleMania moment in 2015 when he cashed-in his Money in the Bank contract against Roman Reigns and Brock Lesnar and became the first Superstar to ever cash-in at The Grandest Stage of Them All.
What if Lesnar wait till 'Mania and then unleash his attack on Rollins? After all, he often does surprising things. For instance, beating our favorite Superstar in mere seconds. Or winning the Universal Championship (and Money in the Bank briefcase) despite the backlash.
Lesnar and Vince McMahon reportedly had a verbal fight at WrestleMania 35 over the fact that the former wasn't going to main event the show. So he decided to be at first instead. Vince knows Lesnar's importance and it's why he might allow him to be in another main event of 'Mania. Just like Rollins, he could also cash-in his briefcase at WrestleMania.
It has happened before, and I agree with it. But almost everything in pro-wrestling has happened before, one way or the other.