#1 John Cena (WrestleMania XXX, 2014)
The first loss. Some come back from it stronger while others crumble. Some just keep moving forward. In the case of Bray Wyatt, it goes deeper than that. Wyatt, along with Harper and Rowan, was untouchable from July 2013 through March 2014. Eight months of destruction may have put fear into the hearts of most of the roster, but not John Cena. More importantly, the preiod didn't put confidence into Wyatt. He talked a big game but when it came time to win, he couldn't finish the job.
WWE went in an interesting direction with this feud. Wyatt spent weeks trying to convince Cena to embrace his dark side, to show that he was a monster. The Eater Of Worlds told Cena that he knew the last decade had been just a facade. The Cenation Leader wasn't truly a "shake the hands, kiss the babies" kind of guy. He did it because it made him popular and made him money.
He was right. John Cena never admitted to it. WWE, via the commentary team or otherwise, never admitted to it, but he was right. Cena had a dark side. A very dark side. A dark side that he embraced for years and used to help him win and defend championships. Cena was brutal with both his words and his actions. That is why this rivalry was so problematic. Was Wyatt simply trying to remind Cena of something he had decided to forget, or were they rewriting history and acting like the record champion was a complete saint and always took the high road? Brilliant (poorly done, but a brilliant idea) if the former, or frustrating (at best) if the latter.
In any event, Wyatt failed to get Cena to embrace the hate. Cena, at one point in the match, held a chair in his hand while The Eater Of Worlds kneeled, in the middle of the ring, begging Cena to use it. The Cenation Leader looked conflicted and maybe a little bit upset, but decided against using the chair.
Wyatt was in his head. Sadly for him, his mind games were not strong enough, and Cena was able to defeat him. This was Bray's first big match, and not only did he fail to win, but he did so while applying mind games and employing his family members for help.
If you work backwards from his team with Matt Hardy, every weave, twist, and turn will come back to this loss. Every time he needs to win, he gets desperate and does something self-destructive. This was the start. This match was why his successful journeys last only very briefly. His confidence, which was already frail, was shattered. It's happened over and over throughout his career. Hopefully, The Fiend is the beginning of a new Bray Wyatt. Time will tell.