Naval combat, which is just kind of meh.
Of all things, this is the one that most impresses me negatively. Not only the naval combat is bad: everything related to the ship is bad (especially the combat, of course).
In PoE1 the stronghold was the weak point. In PoE2 they screwed up the SAME THING! Seriously, I wonder how the hell the naval combat and the mechanics of the ship were approved and someone said "man, this is pretty good, let's release". At some point someone APPROVED this. HOW?????????
It wouldn't be so bad if they wouldn't have constanly talked about the ship before release. The ship combat is a bad joke it's boring too slow and feels like something an intern made within a week.