Cheney as Colonel Kurtz (from :30 to 1:30): "Horror and moral terror are your friends. If not, they are enemies to be feared":
More honorable mentions after the jump:
A reader writes:
The key aspect of Cheney which eliminates most evil film protagonists as descriptors is his place behind the throne. He isn't Sauron, Palpatine or Voldemort, all of whom were the face and inspiration of their movement. Cheney without Bush wouldn't have been nearly so effective. To me, Cheney is Grima Wormtongue, an errand boy whispering poison into unwary ears:
Lastly, Cheney as Kaa from the Jungle Book:
A big thanks to everyone who submitted.