This is where a character is shown to have a very scary, thuggish face -- mostly for comedic purposes. The expression will often include a Kubrick Stare, where the face tilts down but the eyes look up. The face of a thug is so scary that normal people are shown to be easily scared off just by looking at them, and can make even tough brutes feel uneasy. Please note that it doesn't necessarily mean "ugly", even though most of the examples below are. It's more about looking threatening than actually looking bad, and it's possible to look both handsome and fearsome.