The perfect villain?

[Caiphon]

Hey guys!! I was wondering how was your approach to villains in dnd, feel free to share concepts, fluff or abilites so we can achieve the most terrifying villain, or the most brutal, or something like that.

C.

[KellKheraptis]

Look up Azriel's Thrallherd.  Or my Mind Mage.  Those should scare Pun-pun even

[awaken_D_M_golem]

Me

Caelic's Boogeyman

Yugoloth-ic version of the Omniscificer.
It knows more about you than you do.
It knows exactly how much to mess with your head,
but still lead you around like a cow with a nose ring.


People fear Chaos, and start killing their own society just to prevent it.
Slaads and Demons have aims people can NOT understand.

[sirpercival]

My personal favorite is the Binder/Ur-Priest/Divine-adapted Anima Mage.  Bind Astaroth, sacrifice people for Dark Craft gold & XP, and manufacture a legion of doomsday devices. 

[GMarshal]

The best villains are those that are tied to the PCs personally. There is nothing quite as gratifying as having the paladin break into the temple of hextor and interrupt the sacrifices,  confronting the six armed iron monstrosity that the PCs have been hearing about in hushed whispers. Only to have it take off its mask to reveal that its the paladin's brother. (Incidentally, 6 poisoned attacks per round and ridiculously high AC is rather nasty to deal with) 

Great villains have build up, having the PCs already informed through contradictory rumors about how terrifying and powerful the villain is makes the fight all the more intense. Oh, and mind control magic, pitting the PCs against each other is also fun :-P .