Since the dawn of wrestling, there has always been a face and there has always been a heel. Without a heel, there can't be a face. That's why it's so important to have heel turns in wrestling.
Sometimes you can see heel turns coming from a mile away, but the best ones happen when you least expect them to do so. Many fans believe a surprise heel turn could happen at WWE's Clash of Champions this Sunday, with either Shane McMahon or Daniel Bryan turning.
Fans, however, are undecided as to which superstar will turn heel, so with this in mind, here's a look at five of the most shocking heel turns in WWE history.
Sami Zayn saves Kevin Owens
One of the more recent surprise heel turns has to be of Sami Zayn helping Kevin Owens avoid Shane McMahon dropping down on him from the top of the cell in their Hell in a Cell match in October earlier this year.
Zayn joining forces with a longtime rival came completely out of the blue and shocked everyone watching the event, pulling him off the announce table and to safety from what would have been a damaging blow from Shane who leaped from the top of the cell.
Shane-O-Mac has been mad at the two ever since and this looks set to continue when he special guest referees their tag team match alongside Daniel Bryan against Randy Orton and Shinsuke Nakamura this weekend at Clash of Champions.
Mark Henry fakes his retirement
During a usual Monday Night Raw in June 2013, Mark Henry came down to the ring wearing a nice pink suit and with tears in his eyes, as he announced to the WWE Universe that he would be retiring from wrestling.
The moment was sold really well, with even John Cena, who was WWE Champion at the time, giving him the title to parade around the ring with. The line 'Baby I'm coming home!' sold it to the crowd as well.
However, as Cena hugged him, Henry picked him up for a World's Strongest Slam, turning heel in the process and the arena exploded in shock. The two would go on to feud with the WWE title on the line with Cena coming out on top.
Shawn Michaels and the Barber Shop
It was a heel turn that helped Shawn Michaels transform from tag team superstar to WWE legend, but it was still a shocking heel turn at the time which nobody expected in December 1991.
All seemed fine when HBK shook Marty Jannetty's hand, keeping The Rockers together, but then moments later, he delivered a Superkick to his former tag team partner and then threw him through the glass window of the barber shop.
It shocked the crowd at the time, but it ultimately allowed Michaels to develop into a singles star and become one of the greatest superstars the WWE has ever seen.
Vince McMahon becomes Mr. McMahon
Not only is this one of the most shocking heel turns in WWE history, it is also one of the biggest moments in sports entertainment history because of everything that happened before and after Vince McMahon ringing the bell on Bret Hart to cost him the WWF title despite the fact he was never pinned or submitted.
Afraid of Hart walking out of WWF to WCW with his title, McMahon called the bell in the middle of Hart's match with Michaels at Survivor Series in 1997 while the Canadian was in a Sharpshooter. Hart hadn't tapped out though, so the bell never should have rung.
Vince McMahon became the evil Mr. McMahon on this night, turning himself into a villainous authority figure that did whatever he could in order to get his way throughout the Attitude Era, and fans legitimately hated him for what he did to Hart.
Seth Rollins destroys The Shield
One of the most shocking stable breakups in recent years has to be that of The Shield in 2014 just after they had defeated Evolution at Payback. The team of Roman Reigns, Seth Rollins, and Dean Ambrose looked strong and unbreakable.
However, when Triple H, alongside Randy Orton, came down to the ring and announced 'There's always a Plan B,' this was when Rollins smashed a chair into the back of his former Shield brothers, breaking up the unit.
The trio would not reunite again as The Shield until earlier this year back in October, over three years on since this shocking heel turn by The Kingslayer.