#1 Isn't friends with: Chris Jericho
This may be another case of since being forgiven, but Chris Jericho did not get on well with the Deadman when he started in the WWF.
Debuting in 1999 during a promo by The Rock (which Jericho has admitted he hates, calling it the Jericho Curse), the future Undisputed Champion next set his sights on the Deadman.
Calling The Undertaker boring, Jericho did himself no favors, immediately getting on his bad side, as well as developing major heat backstage, as most still considered him a WCW star, who had publicly insulted a legend of the WWF.
Things do seem to have eased off though, with the pair facing off multiple times in their careers, and Jericho even winning the World Heavyweight Championship from the Deadman in 2010, admittedly thanks to Shawn Michaels.