7-0 and 12-0 Kane (WrestleMania XIV and WrestleMania XX)
The Undertaker has faced his storyline brother, Kane twice at the grandest stage of all and came out victorious on both occasions, thanks to the tombstone piledriver.
At WrestleMania XIV, The Undertaker delivered the move thrice after the Big Red Monster kicked out on the first two instances while on the 20th anniversary of WrestleMania, The Phenom reverted to his Deadman gimmick from the American Badass gimmick and beat Kane.
Kane is a multiple-time tag team champion and a former World Champion. He has accomplished almost everything in the business and holds the record for most eliminations in the history of Royal Rumble (43).
Kane has been a loyal servant of WWE and has put over a lot of young talents. He is still an active member of the WWE roster where he is wrestling for the Blue brand, SmackDown Live.
8-0 The Big Boss Man (WrestleMania XV)
The Undertaker made it 8-0 when he beat Big Boss Man inside the Hell in a Cell. This was also the first time a Hell in a Cell match took place at WrestleMania. After the match, Boss Man was hanged from a noose by The Brood (a stable involving Gangrel, Edge and Christian).
After his match against the Deadman, Boss Man disappeared from WWF and was assigned to train the developmental wrestlers in Ohio Valley Wrestling (OVW) before he was released from WWE in 2003.
A year later, Boss Man (aged 41) died due to a heart attack at his home in Georgia. He was inducted into the WWE Hall of Fame in 2016.