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.
(..) Hold it, clowney. Keep your paws where I can see them. Gunman #: Don't move. I'll blast a hole the size of a Kansas City watermelon through your ugly ass, Bozo face. What the fuck is that supposed to mean? Go grab that other asshole out of the shitter - and drag his ass back in here. (..)2003 House of 1000 Corpses