CHARACTERS
Seo Eun Ki was quite interesting at first, because she was so different from the usual kdrama FLs, I loved and hated her at the same time - she was strong and clever, but so arrogant, spoiled, had a bad personality and went through episodes of pure agression. Sadly, in the second half, she became rather dull, too swooned by Kang Ma Roo and started to resemble a lobotomy patient.
Kang Ma Roo, to me, is a very depressed character, who can be sweet, if he wants to be. His intentions are a mystery to me. He acts like he cares for the people close to him, but also deliberately hurts them. The love he shows, does he pretend it? That's also what makes this drama so interesting - you are always so unsure. But in the second half, it didn't make sense to me how he could suddenly love Eun Ki, other than pitying her. They were hardly ever sincere. Can there be a love without trust? If manipulation was a love, then there would be many romantic scenes.
Speaking of manipulation, Han Jae hee is a manipulating witch. She only "likes" people when she can use them. She is a character, who is evil, because she wants to be rich, but it's understandable, since she grew up in poverty. She is so self-absorbed. Still, we also get to see her sensitive side and sometimes I even felt bad for her.
Kang Cho Ko was sometimes annoying, but overall she's ok.
Park Jae Gil is like a bright star in all this melodrama. He is the only one who didn't feel toxic to me.
The lawyer felt like a friend to Eun Ki and you cannot convince me, that he loved her (definitely a plot thing).
Eun Ki's father was controlling and mean man. Nevertheless, Eun Ki was so sad when he left, as if he was a loving and supportive parent. Again, I felt like it was done like that solely for the plot.
Overall, the characters were too passive. They were constantly switching between optimistic and pessimistic moods. I needed them to open up more, the neverending lies and them being so ignorant messed up my brain. In the second half, I feel like everyone went insane, being driven just by the desire to meet the ends they want. What I hated the most was how the characters feelings nonsensicaly changed just for the plot.

THE PLOT
It had so much more potential. It has strong premise but its like a tree with shallow roots. The story is so flat: ____. The revenge aspect was very weak, KMR didn't even have any clear plan, he was just waiting for opportunities.
In the first few episodes the story was thought out, but with increasing episodes it started to feel like the writers didn't know how to continue.
There's really a lot of nonsense. In a light hearted drama, it wouldn't bother me as much, but in these serious ones it really does.
There are many aranged scenes for plot to move somewhere. Maybe I forgot what happened, but where did Eun Ki's sickness disappear? Ma Roo's sister's sickness also somehow dissapeared. Riding motorcycle is Eun Ki's hobby, but it appeared only once, and how does Kang Ma Roo know how to ride one?
They bring something in the story and never use it again or suddenly add something, that there was no hint of before. They don't delve too deep into things that were hinted on (death of Eun Ki's mother, more about Eun Ki's ex, Kang Ma Roo's reconciliation with the doctor teacher).
The amnesia part... was unexpectable, but such a stupid, tiring cliche. It felt like something to just fill the time. They could have just made it standart 16 episodes drama.
The final ending was very quick, without any prior development, this "happily ever after" was not at all what I expected considering the overall mood of the drama.

SOOO SLOOOW
This drama has major problem with it's pace. There were many flashbacks, long shots of people walking, standing, thinking or staring... Even the recap+intro was sometimes like 5 minutes long.
Kang Ma Roo is always staring with stony blank face (not that it didn't make me feel anything, but there were just so many of these stares).
Finishing the last 4 episodes was a hell and I would have dropped it, but i have a sense of completion. There was nothing I could look forward to, only the end. I found out several characters speak really slowly, in the later episodes I even watched it at 1.5x speed and some lines sounded like a regular speed of speech.

MUSIC
The OST was average, the music became quite depressive overtime. Also, some english songs in korean dramas feel a bit wierd. However, I liked the opening, it was simple but gripping.

MY FEELINGS
I have to say that it this drama is VERY overrated. I might be a minority, but I think it's not worth the time. I genuinely cannot understand, how people can give it a 10. They are either beeing too kind, masochistic or like everybody in the drama, they must be too in love with ML, to see the nonsense.
I had high hopes for this drama, especially because of the ratings. The story it could be was merely a nice dream. I was wainting for the point when it would get so amazing, but that never happened.
This drama did not even make me cry, although it messed up my brain, made me question myself and got me depressed. But I have to give it props, for being one of few dramas to make me so angry.