#2 Aleister Black

Not long ago it was being reported that WWE has plans of turning Apollo Crews heel. Given the massive fandom that he's come to enjoy of late, I don't really know if the company will go ahead with the originally intended plan. However, if they decide to do so, then Aleister Black would be the perfect opponent for Crews.
What if Apollo Crews turns heel?
Aleister Black might not have a highly vocal connection with the fans, but he certainly has his admirers. The Dutch Destroyer has been booked very strongly for more than a year now and only since Money in the Bank have we seen him hit some bumps during his journey. Thus, he will act as the perfect foil for Apollo Crews.
Black might be embroiled in a feud with Seth Rollins and his disciples right now but once he's done with that, WWE must put him in a title picture because that seems the logical step after months of booking him strongly. And since Drew McIntyre seems to be having his hands full right now, a run for the mid-card title, i.e., the United States Championship seems imperative.