#2 Turning Seth Rollins heel

Seth Rollins had a hell of a year in 2019 and a lot of that had to do with his surprise victory over Brock Lesnar at WrestleMania 35. Not only did the match launch Rollins back to the top of WWE's mountain, but it also birthed his run as The Beastslayer, which was fun to watch.
And then WWE went a step further by making him by a fighting champion and having him compete weekly. This helped a lot in keeping the Universal Title relevant at each pay-per-view and allowed Rollins to accumulate a considerable victim count during his title reign.
Look who just shut down all of Tony Khan's critics! More HERE.
WWE even had Rollins face Lesnar a second time for the Universal Champion, which only seemed to cement his legacy as The Beastslayer after he won again. With that being said, this also marked the beginning of the end for Rollins's run on top, as it was the first time that fans had started to turn on him.
Maybe that had to do with how dominantly he was booked throughout his title reign, or it could just be how many Superstars he held back in the process, but the result was still resentment. Unfortunately for Rollins, all that resentment was evident at Hell in a Cell when he retained The Universal Title against The Fiend after the referee was forced to stop the match
If nothing else, this angered the WWE Universe more than anything else could and they let the company know about it. In fact, that singular moment, along with the backlash that it caused, could be single-handedly responsible for WWE finally turning Rollins heel at the tail end of the year.