#1 Roman Reigns defeating The Undertaker at WrestleMania 33

It was the shot heard around the world.
It was probably the most unbelievable moment in recent WWE history and while IT solidified Roman Reigns as a top tier star for years to come, it also left a big hole in the heart of The WWE Universe. A hole that will seemingly never be repaired after The Undertaker retired at the conclusion of WrestleMania 33.
Not only did this rub The WWE Universe the wrong way, it also completely ruined WWE's plan to make Reigns the new top babyface of the company. WWE even ended up being forced to take Reigns off the television so that the heat could die down enough and they could start building him as a babyface again.
In the end, the match and the result failed to accomplish what it set out to do and that's why its here on the list. The match made Reigns a huge villain for the WWE, completely halted his push for several months, and gave The Undertaker what had to be one of the worst send-offs in WWE history. Just an all around the bad decision and WWE will probably pay for it for years.