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.
(..) to come out here, please? You nigger lover. There's no need to be afraid of him, son. He's all bluff. Nigger lover! There's a lot of ugly things in this world, son. I wish I could keep 'em all away from you. That's never possible. Ifyou wait till I get Scout in bed, (..)1962 To Kill a Mockingbird
(..) in her lap under her shawl... and she'll kill you quick as look at you. Come on. - Hey, Miss Dubose. - Don't say "Hey" to me, you ugly girl! You say, "Good afternoon, Miss Dubose." You come over here when I'm talkin' to you! You come over here, I said! (..)1962 To Kill a Mockingbird