One of the single-player games I'm currently on is Deus Ex Human Revolution, which I think I'm nearing the end. I feel that the development process here was too unfair because in all reality, HR is a fantastic game. The way the player can upgrade Jensen's abilities however he likes and focus on many different playstyles is incredible. The different ways to acomplish a single objective, by hacking, shooting your way in, sneaking through vents or even go invisible is amazing but a single aspect of the game kills the entire experience: The boss battles.
The boss battles, in my opinion hinder completely the overall experience of the game. The force you to take on lethal methods and use guns to kill them. For someone who's focusing on sneaking by, hacking and not being seen, like me, this is really uncomfortable. I'm nearing the third boss fight and I'm scared that I might not have enough tool to take him down, but still I'm very excited about the rest of the adventure. This game really is amazing outside bosses.