#2 Defeating The Undertaker at WrestleMania
The Undertaker lost to Brock Lesnar at WrestleMania, spurring The Beast Incarnate onward to many career milestones. He would subsequently lose to Roman Reigns much to the dismay of the WWE Universe. For Rollins to be seen as 'the guy', he needs to dethrone The Undertaker at WrestleMania. What better stage than WrestleMania 35?
Rollins should compete with The Undertaker in a potential retirement match at the event. If Rollins were to become the man who retired The Undertaker, it would help him ascend to new heights. It would become a part of his myth and his legend.
As we've seen in the past, The Undertaker is not opposed to doing the job at this stage of his wrestling career. I'm sure he knows and understands the value of Rollins and would not be opposed to taking the pin for the benefit of the business.