Vocabulary
최선을 다하다
do one’s best
Meaning
최선을 다하다 — An expression meaning to make every possible effort toward a goal.
Why this form?
열심히 하다 (“work hard”) stresses diligence; 최선을 다하다 stresses doing everything one can.
Examples
정말 최선을 다하고 있다. — He is really doing his best.
끝까지 최선을 다할게요. — I will do my best until the end.