I think the most violent scene is any rape scene, arguably the most dispicable/violent act other than murder (I personally think it's worse). I particularly hate Noodles raping the woman in "Once Upon a Time in America."

-A Streetcar Named Desire-

Stanley: You want a shot? (offers liquor)
Blanche: No, I rarely touch it.
Stanley: There's some people that rarely touch it, but it touches them often.