This one is just bloody terrifying full stop. Monsters hiding in closets or under the bed are a thing of nightmares for most kids. A skeletal type monster with crazy hair would definitely terrify me as child.
Frankenstein (1931) Boris Karloff Especially noticeable here is the sunken in nature of Karloff's face. This was aided by his ability to remove an entire row of dental work on the right side of his jaw. Neat!