JKII's arch-villain should have a history of conflict and death. His/her path should be littered with corpses - and this should be made known up front, IMO, as it was with Vader.
This is Grand Admiral Thrawn
Never give in--never, never, never, never, in nothing great or small, large or petty, never give in except to convictions of honour and good sense. Never yield to force; never yield to the apparently overwhelming might of the enemy.
Winston Churchill, 1941.