The most important Korean figure i think is Yi Sun sin.

Yi Sun sin was born in April 28, 1545 and died in December 16, 1598 by a single bullet in the Battle of Noryang Point in December.

Yi Sun sin (also known as Lee Sun shin) was a Korean naval leader who has defeated the Japanese navy during

th Japanese invasions of Korea (1592-1598). During the Joseon Dynasty he led his victories as the first commandant of the Gyeongsang, Jeolla, and Chungcheong provincial navies.

Yi Sun sin is mostly known for his innovative use of the turtle ship which is the world’s first armoured warship. The turtle ship has greatly helped the Korean navy to win in the battle with the Japanese navy.