#4 Seth Rollins

Rollins has had a very interesting 2019. The Kingslayer started the year by winning the Men's Royal Rumble and would go on to conquer the beast, Brock Lesnar at WrestleMania 35. Rollins hasn't been the most popular on the roster for quite some time now. The Architect's social media outburst coupled with the lack of creative direction have led to fans souring on the man. Despite being a Babyface, Rollins has been getting booed by the fans.
Many are excepting Rollins to turn heel shortly. While we have seen a few flashes of The Architect's turn to the dark side during his feud against The Fiend Bray Wyatt, he is yet to fully turn heel as of this writing.
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Rollins and Styles have already had a MOTY contender with their Universal Championship match at Money In The Bank. Unlike most of the other opponents on the list, the feud between Styles and Rollins would have to be a slow burn, something which is built over the next few months and culminate in a match between the two at WrestleMania 36. This feud, if done properly, has the potential to be one of the best in recent memory.