an 'ugly duckling' that has become a beautiful swan [=an ugly/unsuccessful person or thing that has become beautiful/successful]
('informal') That dog of yours is '(as) ugly as sin'. [=very ugly]
The house is an 'ugly duckling', but it has a lot of potential.
(..) Go. Get to the chopper. Oh, shit. He couldn't see me. Bleed, bastard. You're one ugly motherfucker. Bad idea. Come on. Come on. Do it. Do it. Come on. Come on. (..)1987 Predator