Halo 3 because of Johnson. One of the saddest moments in gaming. One of the few people to ever be called friend by the Chief, and he survived the entire Covenant War, from the very first to very last battle, only to be stabbed in the back a supposed ally. I feel like I should say Halo 4 since because of Cortana, but I've been saying that she was going to go rampant and screw us over since Halo 3, and between slowing me down in Halo 3, to 'accidentally' waking up the Diadact, to trying to steal the Mantle of Responsibility from Humanity, I have no sympathy for her. Halo: Reach was sad, but you knew they were going to die going in and because it conflicted with so much established canon it was harder to get [i]as [/i]invested in the characters.