I think I would also add something like Moorcock's Breakfast in the Ruins. Whether or not it is sf depends entirely on one's definition of that term, but this one deals with "alternative lives" of the character Karl Glogauer, from the past to the future, which is certainly a theme sf has explored quite a bit. At any rate, the novel is subtitled "A Novel of Inhumanity", which should certainly give an indication of the tone.
One thing I would like to address, however, is that all the suggestions I have made also tend to be very concerned with ethics and morality, at their core. The violence and inhumanity is not there gratuitously, but serves a larger purpose. I think, in the main, this is true of any good art; but it is often overlooked because the violence is so "flashy", and a lot of people do tend to take the surface for the substance....
