걸작이 · 걸작을
masterpiece
Example
많은 사람들이 그 그림을 화가의 최고 걸작으로 꼽아요.
Many people consider that painting the artist's greatest masterpiece.
Word parts
걸 outstanding+작 work
Literally 'outstanding work'.
Good to know
Pronounced [걸짝]; casually 걸작이다 can also mean something is hilarious.