> Among the Affront's technological accomplishments is an aptitude for genetic engineering, which they developed long before spaceflight. They use this skill almost exclusively on 'prey species', which tend to be changed so as to provide greater sport (and opportunity for sadism) during the communal hunts forming a major part of the Affront culture.
> One of the few changes to their own species was the redesign of their females to make sex painful for them
> "a never-ending, self-perpetuating holocaust of pain and misery"
I'm curious: do you honestly believe the Affront are cool?
Affronters are just more alive, more vital, actually trying, actually risking things; than the Culture HR department drones (heh), as comprehended by the ambassador, but it's still weird because the ambassador's actions are viewed from the confused uncomprehending PC perspective throughout the book.
Hurting other sentients, just because you're sadistic and/or sociopathic, is bad.
There's nothing vital in genetically modifying women to feel only pain when having sex... unless you disagree?
They're abhorrent, obviously, but one of Banks' better examples of an alien morality. He wasn't really great at this in general; most of his other villains are some variant of evil empire/evil capitalist, or occasional ineffable great-old-one-style evil. For weird aliens (though little else), try Peter F Hamilton.
I think most of Banks' 'villains' were quite appealing in their way (possibly not the pro-Hell side in Surface Detail; I think that's the closest he came to pure incomprehensible evil.)
Given how the culture ambassador is rewarded by being given an Affront body so he can indulge in Affront culture on even terms, and that the Affront are basically psychopathic Bertram Wooster-types, Banks knew that there was some people couldn't help but love the Affront. Something in humans loves it. Like looking at a file of red wool coated infantry (btw, did you get that the Affront is coded for the British empire?) and thinking "yup, really cool".