the very darkest and yet most hilarious things i've ever read are the sick stories of ambrose bierce. (like my favorite murder, an imperfect conflagration, or, god help us, oil of dog). amusingly enough, these are often characterized as "tall tales," or even "tall tales of the old west": if you came looking for pecos bill, you'd be in for a rude awakening; that's why i'm going with "sick stories." obviously they owe a lot to swift, though swift in his utmost biliousness could have conceived nothing quite like this. bierce wrote a bunch of stories in this vein, each better than the last.
i think their amazing satiric bite comes from their routineness, which constructs an audience. the narrators just assume that they are speaking to an audience of thieves, murderers, animal-torturers, and ministers of the lord. that is, the stories of bierce characterize the society around him, the american reading public, his very own audience, as crazed psychopaths living just beneath a surface of highly polite, decorous appearance, a punctilious observation of social norms, the niceties of law or business coupled with perfectly routine mass murders. it's not only that that's what people do in the stories; it's that in writing into the world he creates bierce just blandly continuously implies that we are precisely the same.
one way to think about this in in terms of war. bierce was at shiloh, chickamauga, sherman's march across georgia, and war of course is the great theme of many of his short stories. what he took himself to have seen was the utter darkness behind the facade of civilization: his great theme.