#3. Braun Strowman
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Braun Strowman would have been a great opponent for The Undertaker in 2017 or 2018. Strowman was so hot in 2017 and 2018 that he could have easily defeated The Undertaker and fans wouldn't have been as mad about it.
However, we all know what the story of Strowman's career has been before WrestleMania 36. It was one of a man (or in this case, a monster) who came close to the top of the mountain on many occasions, only to fall short. While in the storyline, it could be attributed to Strowman not performing under the bright lights, the reality is that it was WWE officials who preferred other Superstars to him and used him as a tool to elevate others.
By sheer circumstance, Strowman went from having no match at WrestleMania 36 to defeating Goldberg and finally capturing the Universal Championship. The Undertaker isn't necessarily brand-restricted, so the match is still possible.
But at this point, WWE doesn't have much of an incentive to book the feud.
Major rumor about recently released stars HERE