#1 The arrival of The Shield
By 2012's Survivor Series, WWE Champion CM Punk had held the title for a year. This included multiple feuds with top superstars in the WWE including Alberto Del Rio, John Cena, Daniel Bryan, Chris Jericho and Dolph Ziggler.
During the RAW 1000 show, it became clear that it was only a matter of time before The Rock would challenge Punk for the title.
WWE used different ways to make Punk get his way in Championship matches, once even involving a referee - Brad Maddox to cost Ryback a match inside Hell in a Cell.
It eventually came down to a triple threat match at Survivor Series 2012, between Punk, Ryback and John Cena. Towards the end of the match, three men appeared from the crowd in black turtlenecks and powerbombed Ryback through an announce table.
While the match won't be remembered for Punk retaining his Championship, we saw multiple instances of wrestlers getting beat down by the ‘Hounds of Justice’ known as the Shield, over the next year. Little did we know at the time that WWE in 2017 and beyond would be built upon these three men, who arrived with such aplomb.