#3 Brock Lesnar
It's difficult to predict exactly how the WWE Universe would react to Brock Lesnar defeating The Fiend, which may be the perfect reason for the company to do it. It could create a level of nuclear heat not seen since Lesnar defeated The Undertaker at WrestleMania XXX and serve as another one of the most shocking moments in WWE history.
That could be the shot in the arm that the WWE Universe needs right now. That shock to the system that shows them fairytales don't exist and a man can only stay on top for so long. It may be a hard pill to swallow, especially with everything WWE has achieved with The Fiend so far, but imagine the impact this moment could have.
Again, it may not be a popular move by any means, but the WWE Universe, much like the ending of Undertaker's WrestleMania Stream, could take Brock defeating The Fiend very personally, which could help them get behind whoever ultimately beats The Beast and sends him away from WWE once-and-for-all. Also, having The Fiend lose to a legitimate UFC fighter like Brock Lesnar protects WWE's creation in defeat, which is of utmost importance.
While Lesnar might not be the perfect person to do this and the outcome of the situation will depend on how fans react, he is arguably one of the only Superstars that could reasonably pull it off.