#2 "Demon King" Finn Balor
Finn Balor is one of the most criminally underrated Superstars in WWE. He was the first ever Universal Champion in the WWE, but he had to relinquish the title the very next day due to a shoulder injury. Since returning from his injury, he has lost all the momentum he had.
He is booked strongly only when he is in his 'Demon' persona. But, the Demon King was last seen at the TLC 2017 pay-per-view where he defeated AJ Styles. Balor's alter-ego has not been brought since then.
If The Demon King squares-off against The Undertaker at SummerSlam 2018, we can easily assume that it is going to be an awesome match. Also, it would be a blockbuster storyline with the clash of two unique evil gimmicks. Just imagine the promos which will be the build-up towards the match.
An in-ring performer like Finn Balor can bring out a great performance from The Undertaker. This would definitely be a dream match that will be remembered for ages to come.