한탄해요 · 한탄했어요 · 한탄할 거예요 · 한탄하세요
to lament, to bemoan, to sigh over
Example
그는 젊은 시절을 낭비한 것을 한탄했어요.
He lamented having wasted his youth.
Word parts
한 regret+탄 sigh
Literally 'sigh with regret'.
Good to know
신세를 한탄하다 (bemoan one's fate) is the classic collocation; 한탄 is about personal misfortune, not society.