(These are my opinions, I know that everyone won't agree) ((The actresses are in order, like them just the same))
Gong Hyo Jin - She is the epitome of "independant" female roles in Korean dramas so of course I love her. I feel that she is a bit type casted and that she is in a bit of a slump but her work in the past has been interesting and entertaining! Feels like I don't have to say that much about her, everyone knows who she is and how good movies and dramas she has been a part of.
Seo Ye Ji - Great actress that has showed big improvements! Seo Ye Ji had a bit of a rough start with Moorim School and Potato Star 2017QR3, but I don't feel like it would be fair to blame that on her (the script and concept sucked). She is great with dramatical roles that has some dark plots, she can really stir up emotions in the viewer and stands out in the crowd of bleak actresses. She acted perfectly in the thriller drama Save Me, which is still her best work til date. I wish that she would get more A-list roles, maybe on the next drama by Kim Won Suk (director of Signal and My Mister).
Lee Ji Eun - Also known as IU. Some people won't agree with me on this (trust me I understand that BUT listen to what I have to say). She has done some "bleak and boring" performances in the start of her acting career. She felt a bit distant from the viewer and kind of awkward? But I feel that her role in My Mister alone is enough to prove of her talents in acting. I feel that she will only get better over time because I feel that she just has something that makes people focus on her even though isn't the most expressive actress she delivers one of the (maybe the best?) female acting performance in a drama 2018.
Kim Go Eun - Horror/Thriller queen. I feel that she really hasn't done any bad work, maybe Cheese in the Trap but I feel that was the scriptwriters fault. From a gripping debut in the melodrama A Muse to big hit movies like Monstar, Coin Locker Girl and popular drama Goblin; Kim Go Eun delivers emotional roles no matter what genre she is in. I feel that her innocent and "ordinary" looks makes her a even better actress who can transform into whatever she wants.
Kim Hye Soo - One of my favorites of all time, she can play villains, heroes, the romantic interest and the opposing mother. Her acting career has been filled to the brim with good movies and dramas that shows her ability to portrait anyone she wants. Diverse with a great technique makes you remember her performances for a long time, this is especially prominent in Coin Locker Girl where she acts as the loan shark "Mother".