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.
(..) Go to sleep, go to sleep, go to sleep! Okay, pal, we're gonna get you out of town. No, not that way, not that way! C'mon! Bruce, you gotta work with me! Everybody out! Going to get ugly! I'm sorry. - Damage report. - (bzzzt). - It's comprehensive. Show me something. (..)2015 Avengers: Age of Ultron
(..) There was this...terrible noise...and I was tangled in... in... ...strings. Had to kill the other guy. He was a good guy. You killed someone? Wouldn't've been my first call. But, down in the real world, we're faced with ugly choices. Who sent you? "I see a suit of armor around the world." Ultron! (..)2015 Avengers: Age of Ultron