#2 Nexus Loses to Team Cena at SummerSlam 2010
Nexus is arguably one of the most dominant heel factions of all time in the WWE. Their build up as the anti-Cena division of the WWE that never got an opportunity was incredibly over with the audiences.
The Nexus was booked brilliantly in the first few months of the faction's existence. Just when people thought Nexus had lost, CM Punk became a part of it to defeat John Cena. Things couldn't have been better.
WWE could have been a different playground today had Nexus not been buried by Super-Cena at SummerSlam 2010.
On Chris Jericho's podcast "Talk is Jericho", Edge revealed that both Jericho and Edge wanted the Nexus to win but Cena refused. It's instances like these that have turned people hostile to Cena's influence on the WWE.
But then again, that was Nexus, a bunch of promising upcoming talent who had a lot to prove. Here, we have The Undertaker, a legend who's at the brink of retirement. Even if we assume Roman is as good as Cena at selling out venues, it still doesn't eliminate the possibility of an underwhelming match.
This is especially since The Undertaker is now slightly weak and fragile in the ring. He deserves an opponent who would make him look strong, something that Shane O'Mac successfully pulled off last year.