말았어야

shouldn't have

→ 말다
auxiliary · informal, pluperfect tense Rare #30,223
shouldn't have Used after a verb ending in -지 to say that the action should not have been done.
KO: 그런 말을 하지 말았어야 했어요.
EN: I shouldn't have said that.
Conjugation of 말다
Necessitative pluperfect
말았어야

여기 오지 말았어야 했나 봐요

I guess I shouldn't have come here.

— 이중 배상 (1944)

식당에 가지 말았어야 했다고

I shouldn't have gone to the restaurant.

— 데이 워치 (2006)