Who is the most villainous fictional villain?

To be villainous it is not enough to be merely evil. A cackling Snidely Whiplash twirling his moustache as he – yet again – ties Nell to the railroad tracks doesn’t evoke the sort of epic dismay a truly diabolical villain does. To be a great villain requires a certain panache, aberration which teeters on the brink of nobility… and then topples backward into utter damnation beyond redemption. Think Hannibal Lecter as opposed to Jason Voorhees; Professor Moriarty rather than Emperor Palpatine; Lucifer Morningstar instead of the Cthulhu.

Whom do you believe to be the most villainous fictional villain? Again, not necessarily the most powerful nor the most gratuitously violent, but the one which evokes the most archetypal imagery of villainy.

(PS: If your villain is obscure, please provide a link if you can to something which will inform us.)