Bellyster

Bellyster was the vilest of all the screws at Ankh-Morpork's infamous Tanty. He was the one who wouldn't only gob in your stirabout, but wouldn't even have the decency to do it where you couldn't see it. He was a sadistic misery-monger, hated by all the inmates and his fellow gaolers alike.

Moist von Lipwig did him a disservice during the events of Making Money, for which generations of jailbirds will be thankful. He is actually in the Tanty by the events of Unseen Academicals, where he surely has to look both ways before he does anything in case he is attacked, spat at, kicked, kneed in the groin or he accidentally commits Suicide...