#4 Triple H
Triple H is one of the most successful WWE wrestlers of all time. He has been with the company since the early stages. Today, He is the COO of the company and runs the NXT brand. Triple H has had many legendary matches against The Undertaker.
Also, their Hell In A Cell match at WrestleMania 28 is labeled as 'The End Of An Era'. Triple H has not retired and currently wrestles on a part-time basis. His most recent match was against John Cena at The Greatest Royal Rumble, the same event in which The Undertaker wrestled Rusev in a Casket Match.
Triple H and The Undertaker are set to face each other at the WWE Super-Show-Down event to be held in Australia later this year.
This match could be used as a spark for a long feud leading to WrestleMania where HHH can realistically retire The Undertaker.