Queen of mystery - the main lead might seem a bit irritating at first, but she'll grow on you as you watch more
Live (2018 kdrama) - two female main leads in this one! I loved the older cop lady much more than the newbie, but both of them are strong and determined and the best of their teams..
Stranger - Bae Doo Na was just awesome in this one! You might miss it since it is not tagged as mystery per se.. wait for a couple of episodes before you decide whether to continue watching or not.. it might seem slow to some, but this is an absolute gem of a drama.
Signal - the male leads actually stole the show.. but the female cop does have a strong character.
Voice - again, the male lead (jang hyuk!) was amazing, and the villian (hehe..) was too, but the female lead was just as much the focus and just as determined as them..
Chicago typewriter (female lead in the past was quite a strong character imo)