I've encountered a lot easy bosses. Also they get a lot easier after playing through the game again and again. Easy bosses: Makron in Quake 2. Though he's more challenge without using any power up items, with them he goes down in a few seconds. Alien Queen in Aliens Versus Predator 2 in the Predator episode, she was a bit uhmm.. trying to kill her with plasma weapons -> impossible. Killing her with the combistick -> boring, but eventually she died. Alien Queen was better in the Marine episode. Cyberdemon in Doom3, he only killed me once when I tested how much damage his rockets do. He was more challenging in the classic Doom. Both bosses in Dead Space, once you observe their behaviour a moment, they'll never again hit you. Though, if they hit you, it's probably resulting in death, because then they might hit you again without you having chance to dodge the next attack. I think hardest will be The Legion from Shadowman. Though I think it would be possible to kill him without getting hit, but I'd say it's still quite hard because you need to move. If you stop, his projectiles will hit you (they're homing). He does have some more instant hitting beam attack too, that's what usually hits me, with some luck I dodge it, but I manage to kill him before he's hit me too many times. Soldier of Fortune 1 had quite tough boss too.. first time I managed to kill him was because of some ai bug that made him stand still in front of me without attacking. Never again managed to get the ai bug, so I had to learn how to kill him the hard way. I have a feeling that Descent II might have some tough bosses. I've killed some of them, but I never played to the final boss, except once I cheated there just to see it and the game ending... so I had god mode enabled... Shadowgrounds had quite a tricky boss. I've played it twice through and both times I needed pretty much everything I had to kill him. Also he killed me a lot, but with the 5 continues per level, I was able to kill him with the last life. Silver has a tough boss, neither me or my brother could kill him. We got the first stage of the boss through, but then the player character was already half dead and needed to have a duel with some bad ass demon character.