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.
(..) your old butler. Bang! People from your world... ...have so much to lose. Now, you think because your mommy and your daddy got shot... ...you know about the ugly side of life, but you don't. You've never tasted desperate. You're... You're Bruce Wayne, the prince of Gotham. (..)2005 Batman Begins