Ultra_Extreme said:ye u kill him then reload, and do the last bit of the boss again and spare him. In a way i spose achievements in this case devalue the story.
Also if you got all birds and metals and did not get all the propaganda reports/golden bird award, just randomly redo levels and collect all birds/metals till you get em, its a bit buggy.
oh yeah and playing through with melee only is pretty easy (cept for a few bits) so that achievement is worth it