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.
(..) Two minutes to launch. Just go, I'll be fine! What you talking about? I'm winning. Jarra, you are under arrest for being that ugly... ...and for making that many copies. Surrender! I want him in pieces. Jarra Jr. Is going, going... ...gone! (..)2002 Men in Black II