And the IMDb poll today is on Harry Potter: Who is the most frightening villain and enemy/antagonist of Harry Potter after Lord Voldemort? (poll)
Obviously, of the choices provided, it is Lucius Malfoy...though Snape is currently in the lead. Snape is a tool, a puppet, a push-over (though quite intimidating, he has very little basis). The real power is held by Lucius Malfoy, though he does become a bit of a mockery once sent to Azkaban. In all honesty, Umbridge is the most frightening villain other than Voldemort, but she's not an option.
That reminds me...I have yet to watch Goblet of Fire on DVD...and I bought it on Tuesday! Oh, the horror. The horror.