#1. The Undertaker wanted revenge after Brock Lesnar ended his Undefeated Streak in WWE
The Undertaker reportedly handpicked Brock Lesnar as the man to end his Undefeated Streak at WWE WrestleMania back in 2014. The ending of the streak will no doubt go down as one of the biggest shocks in WWE history.
This was thought to have been the end of The Deadman's career, but after around 15 months, Undertaker made his return to WWE to cost Brock Lesnar the World Championship at Battleground in 2015. Lesnar was about to capture the title from Seth Rollins before The Deadman appeared and sent a message to his conqueror.
It appeared that The Deadman had moved on from this feud when he wrestled Bray Wyatt at WrestleMania 31. But instead, he circled back to his issues with Lesnar which led to an impressive feud over several months.
Following a brawl the next night on RAW, the two men went on to face off at SummerSlam and again at Hell in a Cell. The two matches were highly rated by critics and served as a fitting way for the Phenom to close the book on his rivalry with the Beast Incarnate.