Cruelty and Sadism in literature is a very interesting topic, I believe that even most simple examples - almost complete mannerism, could still be good for your imagination from time to time.
It really doesn't get any better than Marquis de Sade, I rate him among those like Shakespeare and Po and I would even say one day they will be forgotten and Marquis will still be considered modern, almost everything pales compared to him, but sadly most dismiss him as simple pornographer which is of course bullshit.
Coa, I've never dared taste a single fragment from the excremental works of the salubrious Marquis, but I cannot say I haven't always found the odor of his persona to be a musky, appetizing fragrant (and
Quills is really an awesome play and film). Which of his works would be most suitable for a newcomer to his cuisine?
Joko's Anniversary by Roland Topor has some really cringe-inducing scenes of torture and humiliation, but I think the most cruel and sadistic work I've read is Lautréamont's diabolical masterpiece already mentioned by luciferfell:
I shall set down in a few lines how uptight Maldoror was during his early years, when he lived happy. There: done. He later perceived he was born wicked: strange mischance! For a great many years he concealed his character as best he could; but in the end, because this effort was not natural to him, each day the blood would rush to his head until, unable any longer to bear such a life, he hurled himself resolutely into a career of evil … sweet atmosphere! Who could guess whenever he hugged a rosycheeked young child, that he was longing to hack off those cheeks with a razor and would have done so often had not the idea of Justice and her long cortège of punishments restrained him on every occasion.
The scene where the animals of the earth find God inebriated on the side of the road and then proceed to have their way with the defenseless drunkard always leaves me in stitches sweetened with schadenfreude.