#2 Brock Lesnar
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What's there really left for Brock Lesnar to do?
Seriously though! The man has been the reigning, defending, undisputed Universal champion for quite some time now and this isn't even his first run with the belt. In fact, the first time he won the belt, he ended up holding onto it for over an entire year, which effectively destroyed CM Punk's record of 434 days with a major title.
With that being said and Lesnar becoming one of the most despised names in WWE right now and definitely makes sense for him to finally leave the company for good. Not only is that evident by the fact that Lesnar has nothing else to prove, but also due to how much money he has already made with The WWE over the past couple of years.
If nothing else, his clock is ticking for a UFC return and a match with Daniel Cormier and would give The Beast one last accomplishment to ride off into the sunset with. Then again, WWE could always try to court him to stay with them and continue being their part-time champion, but fans are becoming so tired of the gimmick that it almost hurts viewership more than it actually helps.