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.
(..) the other side of the wall? Here you are! Look at me! Focus! Gru? I promise that this wig will transform you from ugly to irresistible. Margo has a boyfriend! And they're going on a date! Date? Boyfriend? What? (..)2013 Despicable Me 2