For me, it has to be Alien: Colonial Marines as it’s terrible due to inconsistent frame rate (moments the game ran smooth and times where lag was insane, even with the best hardware). Both player & enemy AI is crap since the combat wasn’t even that immersive plus Xenomorph AI isn’t as intimidating due to it being poorly implemented.
To my knowledge, Gearbox has never managed to fully shake the allegations that they took Sega’s money for Alien: Colonial Marines and diverted most of it to Borderlands 2.
They also outsourced most of the development to another studio, and covered up that fact before release. After release, they happily pointed the blame away from themselves and onto the other studio, which promptly closed. The whole thing was basically set up to fail.