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.
(..) Hmm... padlock. Listen Cujo, I got some pretty wicked claws under these mitts,... ...do not, I beg of you do not make me bring out these bad boys! It gets ugly! - What are you doing? - Stay back! If I stare at the lock really hard, it'll burst into flames and melt. (..)2008 Bolt