#2 Montreal Screwjob
The "Montreal Screwjob" is widely believed to be a blatant on-screen betrayal of Bret "The Hitman" Hart, who at the time was one of the WWE's longest-tenured and most popular performers of all time.
Hart had recently won the WWE championship in August of 1997, but the news broke that "the Hitman" signed a deal to work for rival WCW in December of the same year. Hart refused to drop the title to Shawn Michaels, who he had a personal grudge against.
So Hart, Michaels and Vince McMahon agreed that the match at Survivor Series would end in a disqualification and then Hart would drop the title at a later date. Vince, however, thought that Hart would take the title to the rival WCW and decided to put the belt on Michaels without Hart's knowledge.
The match went on as scheduled and everything seemed to be normal until Michaels applied the Sharpshooter to Hart and referee Earl Hebner called for the bell at the request of Vince McMahon. Michaels and Hart were just as shocked as the viewers and when Hart realised what happened he was visibly upset and spit right into the face of McMahon.
Hart did not return to the WWE after the screw job for another 12 years, before returning to be inducted into the WWE Hall of Fame.
To this day, the screwjob remains one of the most infamous double-crosses in the history of pro wrestling and a permanent OMG moment.