My first villain was probably the one to inspire the most visceral hatred. I was young and not too terribly concerned with plot, and neither were my players. So they went to Kastle Kojark to prove their mettle and return to the throne room a book from the castle, and Kojark, the kobold master of the castle, invited them in. He told them of all the hideous things he's been collecting for
just this occasion, gives them a
staff of life so they can keep going even after death, and leaves.
And they slog through a fairly illogical dungeon crawl. And blame everything on Kojark. And keep a running tally of how he will die and what interesting mutilations will happen to his corpse. Like I said, visceral hatred.
Other baddies have inspired more subtle and mature hatred. My Eberron game has a lot of these. Slogar d'Cannith jumped to the top of the list. An influential member of an influential family, he considers warforged tools for House Cannith to use, and feels no remorse for supplying thousands of gold worth of equipment to an insane murderer cobbling together a warforged golem from fresh parts. The Freelance Police (read, the party) caught the murderer, of course, but couldn't prove Slogar's involvement. They're all just itching for an excuse to kill him and claim it was self-defense...
Testament said:
Balabar Smenk, from the Age of Worms, has leapt to the top of my PC's hate list owing mainly to his obnoxious, condescending, Jabba the Hutt like manner. He invited them to his place for dinner, and took every opportunity to lord it over the PCs with shows of wealth and reminders of his power. They managed to restrain themselves from leaping over the table and beating him to death with their spoons only though supernatural willpower. They know they're being used, they know that he knows that they know (wtf?!), and there's pretty much squat they can do about it, since this pig owns the freakin' town.
Hey! My players hate Balabar Smenk too! Just the sneering preening illustration was enough to get their tempers up, but once they actually had to talk to the creep they got really mad. The dinner party ended with the PCs telling Smenk to his face how loathsome he was, and Smenk smirking because there's nothing they can do about it.
Demiurge out.