Before Orton had the opportunity to follow through on a planned heel turn, he wound up injured in his first match on Raw after jumping brands. Whilst that shouldn't be a CMOA, it lead to Orton giving weekly news updates on the status of his injury as if it was the most pressing story in the WWE.
During his match with Mick Foley at Backlash, Randy Orton proved to be pretty hardcore when he let Mick drop him into a pile of thumbtacks. The look on Orton's face when it happened tells it all.
As Scott Keith pointed out, even Triple H wasn't crazy enough to do that spot during his 2000 feud with Foley, a feud that might have spilled more blood than any other in company history.
SummerSlam 2004, when Orton pinned Chris Benoitclean to become the youngest World Heavyweight Champion in WWE history, after Orton's mentor Triple H had spent months failing to beat Benoit whilst cheating.
Later on, Orton was told by Triple H to give him the belt or face the consequences. While seeming obedient at first, Orton spat in Triple H's face and officially broke away from Evolution, effectively becoming a face and racking up another CMOA for himself.
At Hell In A Cell 2011, after losing to Mark Henry, Mark tries to put him in the "Hall of Pain" (Mark wraps a steel chair around an unconscious victim's leg and hits it with a second-rope splash). At the last second, Orton revives and dodges the splash, then goes postal on Mark with the chair.
On the 10/14/11 edition of Smackdown, he won a battle royale by last hitting The Miz with an RKO while both are on the apron. They both fall out, but Miz hits the ground first.
On the 12/9/11 edition of Smackdown, he must defeat Dolph Ziggler in seven minutes, fifty three seconds. Despite Wade Barrett's interference, Randy pins Dolph with an RKO with two seconds to spare. Barrett angrily assaults Orton after the match and tries to send him through a table, but Orton fights him off, then powerbombs Ziggler through the table.
At Tables Ladders and Chairs 2011, Wade Barrett positions a groggy Orton onto a table, climbs to the top rope, and goes for a diving splash. Orton pops up and gives him an RKO in midair, sending Barrett through the table.
And then, for added insult to injury, laughs as the ref rings the bell.
At Hell in the Cell 2012, Alberto Del Rio tries to hit him with his step-up enzuigiri. Orton dodges and hits him with the RKO while Del Rio was still falling. It has to be seen to be believed.
Similarly at Money In The Bank 2013 during the titular match, yanking Rob Van Dam off the ladder from about the 10-ft. point and RKO-ing him right into the ground. It was a standout move in a match that already lends itself to a very high Holy Shit Quotient... not to mention it was the move that led to Orton winning the match... and eventually, winning the WWE Title.