ugly duckling
Idiomatic expression referring to a person or thing that initially seems unattractive or unpromising but later develops into something beautiful or successful. Originates from the Hans Christian Andersen fairy tale.
She was an ugly duckling as a child, but now she's a famous model.
This company grew from an ugly duckling into an industry leader.
All-hiragana variant; may appear in children's books or older texts.
Kanji spelling for みにくい; less common but still seen.
From the title of Hans Christian Andersen's fairy tale 'The Ugly Duckling' (Den grimme ælling), translated into Japanese as みにくいアヒルの子.