Ming Lan from The Story of Ming Lan is my favorite female lead. She's not meek or submissive nor is she cocky or arrogant. She's strong but in a realistic way. Because of the historical setting and her social status, she is forced to behave in a certain manner. She knows her boundaries and limitations yet she is smart enough to get what she wants anyway. A brilliant female lead in the most understated fashion.
I also really love - -
Zhou Zhou - My Huckleberry Friends
She's such a chill smart female lead, which is rare in school dramas. They're usually loud or stupid but she was calm and level headed. Super refreshing.
Bok Shil - Shopping King Louie
The most genuinely kind female lead. She was just adorable and sweet. Although she was naive, she wasn't stupid and she always treated the ML with so much kindness and respect.
Chu Qiao - Princess Agents
She didn't have much personality, but it was rad as hell seeing a FL who was such a badass and could hold her own against the guys.