#1 Challenge Brock Lesnar

Now, this one is tricky, because there are so many variables here. Does The Fiend go after Lesnar because he's WWE Champion? If so, that means that Drew McIntyre doesn't go over at WrestleMania - which is unlikely but, then again, we were all sure that Roman Reigns was going to beat him at WrestleMania 34, so... yeah...
That's not to say that Lesnar needs to be champion in order to have The Fiend come after him. In fact, it's probably better if he's not. While it was great to see Wyatt a world champion once again, holding the belt painted the character into a corner, leading to articles like this to have to be written. It would actually be better if Lesnar wasn't champion.
Top WWE star punished? More details HERE
Consider this. The Fiend is coming off this loss at Super ShowDown and then... well, whatever he does at WrestleMania is irrelevant. He still has something to prove and needs to put fear back into the WWE roster. Who better to go after then The Beast?
The Beast vs The Fiend.
The thing is, The Fiend doesn't even have to win any of these matches. Sure, Lesnar F5s Wyatt, like, six times and manages to get a pinfall victory. Five seconds later, The Fiend is back on his feet and Mandible Claw-ing the bejesus out of the former UFC champion. It's just another example of how wins and loses don't mean anything to this monster - only causing destruction and fear.
So, there you have it. Whatever they decide to do, what's important is the story they tell. The Fiend is the kind of character that you can do just about anything with. Let's see what they actually do.