I am a huge fan of Kim Hee Sun's shows (ever since I watched her in Faith) so my review and rating could be a bit biased. I started watching this expecting a melodrama but boy it took a violent and thriller turn too soon (glad I didn't check any spoilers). Both Kim Hee Sun and Lee Hye-Yong delivered amazing performances and complemented each other's characters so well. I loved the quirky MIL character from the very beginning.
How does it feel to live in a carefully constructed, masterfully manipulated fairy tale life for so long, only for it to come crashing down on you? How would it feel when. you realize that your very identity is tied to these lies and facing them means facing yourself? Sometimes life is not black and white and there is just too much grey. Ultimately you need to make the choice of pursuing truth vs protecting what matters to you. Also despite their differences, the family comes together to protect their definition of what's important. That's why it's bitter sweet. I do feel a bit conflicted about Hong Sa Gang's actions regarding her son but ultimately her son was all left to her to. However I don't have as much of a patience for her son (Jae In). He seems irresponsible and spineless for the most part.
The villain is so OP that I am flabbergasted. She is a master manipulator and gaslights so many characters and all her victims remain loyal to her for the most part. That's some fantasy level skills there. But the show stays true to her narcissistic and obsessive behavior. She was so good that it would have been impossible for either NYW and HSG to respond to her by themselves. The show definitely nails down the idea that in the face of a common and powerful enemy most personal differences become irrelevant.

Overall this show is a great watch and I think the pacing is just right.