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.
(..) I'm tired of never having me a buddy to be with... ...to tell me where we's going to, coming from, or why. Mostly, I'm tired of people being ugly to each other. I'm tired of all the pain I feel and hear in the world... ...every day. There's too much of it. It's like pieces of glass (..)1999 The Green Mile
(..) - I'm gonna take you out! - Percy! Percy! You little vermin! I'm gonna stomp your life out! It's just a little mouse, dumb merde. You ugly little piece of sh... HARRY: Are you listening to me? - Fuck! - Percy! - I'm gonna rip your diseased head off... ...you little piece of shit! (..)1999 The Green Mile