#4 John Cena
The Undertaker has had such a remarkable career that he deserves to go out at the hands of another legendary superstar. Enter, John Cena! These two had a very awkward rivalry last year at WrestleMania, which many still believe was left incomplete.
It'll be interesting to see whether these two icons clash sometime in the future again or not, but Cena would be a perfect candidate to retire 'Taker especially considering their history together.
#3 Bray Wyatt
Bray Wyatt and The Undertaker have had a feud previously during WrestleMania 31, but unfortunately, that didn't do much good for Bray as The Phenom quite convincingly defeated him at the Show of Shows.
Bray debuted a new gimmick a couple of weeks ago, The Firefly Fun House. The gimmick portrays him as a changed man who loves kids, but we've seen Bray showing signs of already breaking into a maniac in his promos. Many fans, including me, are very interested to see how WWE plays along with this gimmick, because of the immense possibilities it has.
A feud between The Undertaker and a revamped Bray Wyatt at next year's WrestleMania, ending with Bray retiring the Dead Man would genuinely make Bray the new face of fear.