I don't wanna use that form, it asks for google login it seems.
IMO there are so many good actresses in kdrama that it's almost impossible to mention specific ones.
But when I think of recent dramas that I have watched, these come to mind:
#1: Shin Hae Sun, for Mr. Queen (2020-2021), cemented her status as a top FL actress.
#2: Moon Ga Young, for True Beauty (2020-2021), just amazing and likable actress
#3: Jeon Yeo Been, for Vincenzo (2021), really a memorable FL.
Newcomer relevancy:
Kim Da Mi, for Itaewon Class (2020) , also lead in the movie The Witch, I think she's going to be a popular actress, she surely is a great actress.