Arkham Knight. That game is a steamy pile of shit that missed the mark on both their promises.
1. The Arkham Knight. Devs and writers said he's a brand new character. Turns out, he was just the red Hood all along.
2. The Joker being dead. Yea, sure, he was nothing more than a figment of Wayne's imagination, but my god. The game was more about the Joker than all the others were. It would have been nice to see the Scarecrow actually have the spotlight.
Not to mention the horrible back and forth chasing gameplay. As well as the overuse of the batmobile.
And don't get me started on the fucking sidemissions. Unlocking those were mind numbing. I actually said fuck it and quit.