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.
The disaster of Colonial Marines is well documented. Iirc, part of the issue is that they gimped the Xenomorph AI at the last minute, an issue that has been fixed with mods. Another part, I believe, was Borderlands. I don’t think it was outright proven, but there were accusations that money provided for the development of Aliens was instead funnelled to the development of Borderlands by gearbox.