For me I've gotten all in Borderlands 2, Halo 4, Halo Anniversary, Sonic Generations, Assassin's Creed 2, Lego Marvel Super Heroes, Lego Star Wars 3 and I could've had a lot more but dlc or hard multiplayer achievements held me back. I think my most proud one was Borderlands 2. Getting all the achievements required a lot of dedication. All those dlcs. I must've done literally everything in that game.