Played through this on co-op, and it started off well. I love that you and your co-op partner can go off an explore on your own and teleport back to each other whenever you want. That made me think the co-op was intentional. Once we hit the halfway point though, it because obvious that co-op was an afterthought. Some bosses and areas rendered one player completely useless (or a liability). The final boss had abilities that one player had no way to avoid. And we couldn't finish the game with both of us, one had to leave in order to be able to land the final hit. Achievements were entirely disabled in co-op. Really just very frustrating and mean with design choices.