11-0 Big Show and A-Train (WrestleMania XIX)
This was the only instance when the Undertaker was involved in a Handicap match at WrestleMania as his scheduled tag team partner Nathan Jones was removed from the match beforehand. Taker pinned A-Train after delivering a tombstone and made it 11 wins on the trot at WrestleMania.
This was the Undertaker's last match under the American Badass Biker gimmick.
Big Show is a seven-time World Champion and is still an active wrestler in WWE as a part of the Raw roster. He is scheduled to face NBA legend Shaquille O'Neil at WrestleMania 33 and the world's largest athlete has trimmed down to get in shape for the bout.
On the other hand, A-Train (Matt Bloom) left WWE in 2004 to be a part of NJPW and returned to the company in 2012 as Lord Tensai before he retired from in-ring competition in 2014. At present, Bloom is the head trainer in WWE's developmental territory, NXT.
13-0 Randy Orton (WrestleMania 21)
WrestleMania 21 saw Randy Orton becoming the first wrestler who wanted to face the Undertaker at the grandest stage of all to end his streak (12-0 then). Orton failed in doing so as the Phenom pinned him after delivering a tombstone and made the streak 13-0.
There were reports that Randy was supposed to break the streak but he was hesitant in doing so.
Orton is already a future Hall of Famer, as the 12-time world champion has accomplished a lot with the company.
He earned the right to be the #1 contender to face the World Champion, Bray Wyatt at WrestleMania 33 by winning the Royal Rumble earlier this year and is currently in the middle of a breath-taking feud against the Eater of Worlds.