Let's see...
-Burying the nexus and specifically wade barrett to get john cena over: Big fukk up. Yes, Wade was the only member worth a push but the fact was that Nexus was seen as a threat, were getting ratings and were over. The mistake here was making them look as a non threat as time went on. Cena getting owned and then getting his revenge was the right move that time imo, but the way they did it was full of mistakes and when Juanito finally "won" and beat Wade at TLC, all the heat was gone. After Summerslam it was one mistake after another and WWE trying to put band aids so they could ending in December.
-Pushing the Miz to the moon, ruining wrestlemania, and burying him therafter: I blame Miz here 100%. Before getting the MITB push he was doing very well and improving. He was getting better on the mic, he was at least decent in the ring and he was finally getting SOME heat from the crowd. Then WWE decides to go for it with the guy and this motherfukker goes back to being absolute trash. He fukking chocked.
-Pushing Jack Swagger prematurely, burying him, bringing him back, ruining wrestlemania (in progress):
-Burying red hot Daniel Bryan in 18 seconds to get the fukking brouge kick over: If they would've gave D-Bry and Fella 15 minutes to have a great WM match, Bryan would've ended up in the dreaded mid card limbo. Instead, he was made to look like a fool and the fans got pissed and he ended up 10x times more over than before. The fukk up was not giving him a little title run when he was feuding with Punk.
-Bringing back kevin nash to make bizzare cm punk/hhh/diesel fued with no payout to this day: Huge fukk up. So after a LONG ASS TIME wrestling had a spark, a very small one, but a spark nonetheless. So what does WWE do? Bring Punk back way too soon because they are afraid Summerslam is gonna bomb without him (turns out, Summerslam was a big failure anyway) and have him feud with Kevin Nash for no reason whatsoever. Look, it's very possible Punk was never going to be a big star regardless of how they booked him post-pipebomb but they sure as hell gave him no chance to try and see if the little spark he created could have lead them somewhere. Yes, he ended up fine after Survivor Series and has been their "1B" star to Cena's "1A" but they threw in the bushes something that was very intriguing and they did it for absolutely no reason.
-Using Zach Ryders organically grown heat to get eve and john cena over (who wasnt a heel?) Meh. Ryder was never going to be anything big. If we are honest about every Nexus member besides Wade not worth a damn, then we should be honest about Ryder not having enough to be anything more than a midcarder. He's not very good in the ring and he's not good at cutting promos either. Still, they could've at least made him a more successful Santino and buried him for the #fukkery and nothing else
-Misusing Brock Lesnar when he and cena had MOLTEN heat in may fukking up match with supercena finish: They fukked what could've been a HUGE Summerslam rematch but Brock is still gonna draw if they keep using him part time and making him destroy people every time he is on TV. They botched 1 big PPV buyrate IMO, nothing more.
-Using Randy Orton's constant heat to put over floundering bums like christian and swagger: This is actually one of the few good things they've done in the last few years. Orton's gonna be over no matter what but it's been already proven he wont ever be a superstar on Cena's level (same thing we now know about CM Punk) so WWE's been lucky that Randy is willing to do jobs and put other people over. He's been unmotivated as fukk in the last year but a win over him is still a big deal kayfabe wise.
-Insane misuse if Dolph Ziggler: I don't think Dolph could ever be a huge star. All these jobs he's been doing for the past 2 years wont hurt his chances of being a steady maineventer though, and that's all he can be...and that's fine with me
So yeah, the Nash thing clearly takes the cake for most
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decision they've had in this Era.