The Glory
I think everyone has to agree that this is Song Hyekyo's best role. Not only did she made this her role, she knew exactly what to give. This genre suits her amazingly and shows her capability to act in a genre that is not romance. I've tried watching 2 of her romance kdramas and just couldn't finish it (I did watch Descendants of The Sun, but I did not think it was THAT good). I could feel whatever emotion she was portraying, even the solemn ones. It had meaning, no matter what. With a character like this, it cannot be easy.
The whole cast was acting their asses off. I've never felt such rage with a villain in a kdrama, but since there were literally 4 of them, it's only valid I feel such emotions. So, in other words, the actors' and actresses' did so so well. I did love the romance subplot but was it needed? Not really. Plus, she had more chemistry with the main villain's husband lmao. Anyway, the hype over this series was much deserved.