Usually, the most disturbing death scenes are unsettling not just because they're graphic but also because they're prolonged. The scene that does it for me is Washizu's slow arrow death in "Throne of Blood." What other movie death scenes did anyone out there find unsettling because of how it occured and how long it was?
The arrow scene is great of course, actually I think a death scene earlier in Throne of Blood is quite disturbing too. When Washizu cuts down the murderer who has just killed Miki, and the man is trying desperately to get up, but can't. Just the time Kurosawa takes, as well as the composition; no cuts and filmed from behind, showing the whole room and the man dying in the middle while Washizu backs away from us - great film making! Makes it chilling even though we have absolutely no emotional connection whatsoever to the assassin.
More recent example: Though technically he doesn't die, the scene where Ethan Hawke's character is about to be assassinated in Training Day is one *beep* up sequence (not that the movie overall is all that great).
When i was doing my SATs last year we only watched the scene with the arrows and we were told that the actor had no idea that he was going to be fired at with the real bows. they just took a load of people who were proffessional at firing them and told them to hit a small target. out of them he told them to hit the wooden blocks that were hidden under Macbeths armour. so the look of terror in his face is a true expression :D