대기만성
大器晩成 · a great vessel takes long to finish
Great talents bloom late.
When to useEncouraging someone whose success is slow in coming.
Examples
서른 넘어 데뷔했지만 대기만성형 배우로 성공했다.
He debuted after thirty but became a classic late bloomer.
Korean life dictionary
22 short guides to words and manners