Death of Behn
One of the most disturbing scenes in any movie.
He is wounded by a shell, cries out that he's blind, and is then shot dead by enemy machine gun or sniper fire. Another soldier brings him in, and Kat strongly criticizes the would-be rescuer for risking his life to save a corpse. The young soldiers present get a sober lesson in death, tragedy, trying to stay alive, danger, and the utter fallacy that war is somehow romantic.
Any others?