I certainly hope I'm not a scary person in real life, it's not like people run from me when they see me. People are usually pretty nice when they meet me. If they're scared, they keep their shuddering to themselves. But even if you're a nice person, it's easy to be scary as a character in a movie. All you need to do is devoid yourself of any feeling toward other people and regard them as a piece of meat. If you can imagine eating someone, or if you can imagine that person being dead, that can make you seem pretty scary. But if you want to get technical about it, most of what's scary is in the writing, not in the acting.