#1 w/Team WWE vs The Nexus (SummerSlam 2010)

This is the most unfortunate case of them all, as this had so much potential. The rookies from the first season of NXT all debuted in WWE, as The Nexus, and wrecked everything in sight. Barrett and co. had so much momentum on their side, until they ran into prime 'Super Cena'.
The Nexus was originally supposed to win their 7-on-7 elimination match against Team WWE at SummerSlam before John Cena swooped in and changed the finish. Wade Barrett was made to look like a fool for failing to put away Cena after hitting a DDT on the exposed concrete floor.
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After that defeat, nothing would be the same for The Nexus. Their threat was wiped out and even Cena himself joining the group did not salvage anything.
Barrett could have realistically become the WWE Champion had his team been put over in the SummerSlam main event, but he and the company can only wonder what could have been.
Out of the seven members of The Nexus, only one of them remains an active performer on the WWE main roster. Heath Slater. Also, not including Daniel Bryan who was in their initial attack, the original Nexus members have won a grand total of zero WWE World Championships.
No matter how bad things got for John Cena's opponents, The Nexus will remain his biggest victims. Wade Barrett truly should have beaten Cena at SummerSlam, but he and his followers had their legs cut out from under them.