I haven't yet read any other manhwas, so I can't exactly speak for how it compares to others. I can, however, base my review off of my general reading experience.
Killing, Stalking is masterfully written. I can't believe I waited so long to read it. It's been a while since a story had such complex emotions involved that I couldn't really find the words to explain. It's very clear that a lot of thought was put into it by the author, all the way from metaphors and character parallels to the smaller details, a lot of which likely went over my head. The emotions that the characters feel and their traits and actions are so incredibly complex and human that it's almost like they'll come out of the screen and, I don't know, strangle me? Haha.
I went into this story for the dark erotica and stayed for the writing itself. It's definitely hot if you're the type of person who enjoys dark stuff but it's honestly not the right story if you're just looking to get your rocks off, because that's not purely what it's trying to do (there's no lack of se** art, though.) But I also don't think it's the right story if you aren't looking for that at all, either... I think it sets out to be sexually attractive while also telling a deep and impactful story.
There are no purely 'good' characters, and no purely 'bad,' either. Every character has a reason for acting the way they do. Both of the leads have untreated trauma and mental health issues that I think are handled wonderfully. Their attitudes towards their abusers are very much realistic as well. This story is one with a lot of conflicting emotions.
B** and Sangwoo's relationship is just... masterfully done. The story does a great job depicting codependancy and the complexities of abuse. While they both act in very erratic and odd ways, especially concerning eachother, it just... makes sense in the context of the situation, their pasts, and the way their minds work.