A villain that tends to be seen in closeup.
In film, the closeup is a magnifying device. It highlights details, makes small actions seems gigantic, and narrows our focus to one important subject. When that subject is the villain, then their closeup serves to highlight said villainy. Closeups make a villain scary because we're forced to be closer to an unpleasant character. If he's an ugly villain, we're forced to gaze at all his pores. If he's an intimidating villain then he seems larger and ominous, since for the moment he controls everything on the screen. And if he's often in closeup, then he always seems to be in control. Compare Gross-Up Close-Up and Nightmare Face.