For the first seven episodes this was really good show.
The story was cut and paste, but the lead are effortlessy great, and have great chemistry. It was my first time watching ML, and I thought he really looked the part and was well cast. I know the FL from IOTNBO, and while this role is nowhere as good, she was still very charming and incredibly watchable.
I wasn't expecting much from the series. I just wanted a fun revenge story, and it was delivering that at the beginning.

Unfortunately in E8, one character made such an illogical decision that led to a very serious event. I would have let that pass if what followed had some logic.
Unfortunately, the plot started to become increasingly ridiculous. Characters behaving in such random way just to move the plot. Also, sometimes certain characters were introduced for one or two scenes to provide us with something the leads could use.
There were certain reveals, that made things worse, instead of giving us a shock.
Also, the court scenes were ridiculous. Granted, I am not a lawyer or Korean, but there are some basics.
You might ask why I didn't drop it?
The lead were really good and very watchable, and the show still had some good moments.

I always rate based on the entire series, so on the whole, it was a decent series, but ultimately disappointing.