Nothing can top how bad Kevin Steen got wasted at his hottest. Threw money away for no reason.
The worst thing is that Corny was actually right
in theory, but his execution was all wrong. He wanted Steen gone for six months before the comeback stuff, but that ignores that this would mean six months of a major pay cut and six months without one of the hottest acts in the entire industry. I'm openly biased because Steen saved my love for wrestling twice over (post-Benoit with the Briscoes feud, in 2011 when I gave PWG a real watch), but it says everything negative about Corny's run that two guys he wanted off the shows (Steen and Generico) ended up being two of the bigger deals in the last decade.
Which leads to my actual answer to "what is the worst booking move in ROH history":
Giving Jim Cornette creative power.
Corny regularly forgets, or maybe openly ignores, that ROH was formed not from a plethora of old-school purists, but from the same fans that loved ECW. It was a hot, revolutionary product that respected where the business had come from, but knew it had to move forward, and the best way to stand out during the post-Invasion doldrums was to offer a bleeding edge in-ring style.
He had a vision of the kind of talent that he wanted to showcase, but that vision ignored the workers who were actually drawing an audience in 2012. He wanted to present a gritty, realistic product that took itself seriously, but his way of doing that was to mimic the booking style of failed companies from the last 20 years (including his own).
Say all you want about how lame duck the Adam Pearce shows were, and how there were more moving parts beyond Corny's control than he could have previously imagined, and even how Delirious had the final say (for way too long), but Corny's fingerprints are all over those shows after Final Battle 2011 and are a big reason fans tuned out.