The Babadook - Tim Purcell
Although viewers don't see The Babadook himself much throughout the film, the monster is still absolutely terrifying. Tim Purcell had to sit through hours of makeup for this role. In some scenes, the folks in post-production used CGI to make his face even scarier.
Hannibal Lecter - Anthony Hopkins
Anthony Hopkins is one of the most iconic actors of all time. His role as Hannibal Lecter in The Silence of the Lambs is still revered as a classic. Unlike most scary horror villains, he wasn't in a full costume. He was simply himself, dressed up as a prisoner. The muzzle is iconic, of course, but the rest of his terrifying character is just Hopkins himself.