Hi.
It's "Minikui." If you see this by itself, it can also mean "difficult to see" (derived from "to see" or "miru"). But if Kanji( 醜い) is used it's clear to distinguish the two("difficult to see" is 見にくい), or understanding the context in the sentence.
The world is not used that often. The most well-known one is Hans Christian Anderson's fairytale, The Ugly Duckling. In Japanese, it's Minikui Ahiru No Ko (醜いアヒルの子)。
Ahiru = Duck
Ko = Child
I hope this helps.