#1 Triple H

The third superstar to have defeated both Brock Lesnar and The Undertaker is the COO of WWE, Hall of Famer, the King of Kings, Triple H.
Triple H has faced the Undertaker thrice at WrestleMania but has never been able to defeat the Dead Man. But last year at the Super ShowDown PPV in Australia, Triple H pinned The Undertaker in their No Disqualification match, with some help from two of his best friends, Shawn Michaels, and the Sledgehammer.
Did you know a top WWE Superstar just wrestled outside the company? More details HERE
He then also went on to defeat The Brothers of Destruction alongside Shawn Michaels as D-Generation X in his comeback match at the Crown Jewel PPV in Saudi Arabia.
As for Brock Lesnar, the Cerebral Assassin faced the Beast at WrestleMania 29 in a No Holds Barred match with Triple H's career on the line. In what was a grueling match, Triple H managed to pin the Beast after delivering a Pedigree to him on the steel steps.
Which current WWE Superstar do you think can join this list in the near future? Do let me know in the comments section.