Warnings for spoilers for For Your Murder, as this entire post covers the ending of the manhwa.
I feel like the ending of For Your Murder is hated for the wrong reasons.
Don't misunderstand, I didn't like the ending. Reading it initially, all it left was disappointment. It was rushed, it was messy, and it wasn't the ending most were looking for. But it had some realism in the way Inseop reacted at the end.
The number of posts and comments I see questioning why Inseop chose to end it all the way he did is depressing, because it makes sense, but it wasn't fleshed out entirely enough for everyone to understand.
Inseop's love was fervent, obsession. He initially wanted Gijeong as a sort of object, but he began to develop feelings for her, obsessing over her, isolating her to ensure he could have her. When that didn't work, he physically isolated her, flying her out to some cabin somewhere. This is where cracks started to form in Inseop's character, though understandable.
I feel the concept of isolation and entrapment has been diluted as a result of all the yandere stories pumped out as of recent. It feels like an obligation to "prove" that a character is obsessive enough. Looking at the same action in For Your Murder though, it's a little different in execution, and gives insight to Inseop's deteriorating mental state.
Inseop is intelligent, he drives others to death without having to kill them himself, keeping his hands clean. He knows how to get what he wants, and he will do just that. When Gijeong willingly goes to live with him but neglects her own health in retaliation, Inseop snaps. He gets messy. He leaves the detective's phone and blood. He leaves traces he hadn't before. He was desperate, and that desperation shows not only in his traceable crime, but in his following reaction of flying her out.
Realistically, in other manga/manhwa/manhua, the yandere character is at some level satisfied in keeping their victim away from others. They would be elated, with some derivative of the phrase "I don't wish for your happiness away from me" often being echoed. This does not apply to Inseop, and quite frankly, I don't see it often applying realistically either.
In his desperation, Inseop flies Gijeong out to have some control over the situation, or that's how I interpret it. He is unable to control her actions (or inaction) and looks to any way to convince himself that he still has everything under control. That Gijeong didn't just come to him willingly. That the reason Gijeong doesn't love him back is because he forced her here, and not simply because she hates him for what he's done in his attempts to have her to himself. That he still has the ability to change her mind. That she could still love him.
But she doesn't. Gijeong makes this clear soon enough. By outright telling Inseop that she despises him, and that she would not reciprocate his love in any capacity no matter how much time passes, no matter what he does, Gijeong breaks him.
Think of a character you are obsessed with (if you have such an obsession). For some, thinking about this character brings unfathomable joy, and having everything related to this character is a must. When someone with such a strong obsession is given the reality that they will not own everything related to said character, they may become depressed and harbour suicidal thoughts. This flipping between a near-manic state and depression is what I view as a realistic yandere. It's not the best example, but it's what I could think of without implying such a relationship between real individuals. ;;
Assuming a similar sentiment from Inseop, when given the confirmation that he will not attain what he desires, that his love is not and will not be reciprocated, no matter the circumstance, he breaks his stoic exterior.
Even nearing the end, the artist and author designed Inseop to have a more disheveled appearance, directly contrasting his professional air when dressed as a lawyer. If I could describe it, he begins to malfunction. He attempts to kill Gijeong, only to stop once he sees blood. He does the same after knocking out Gijeong. If he were the ever-so-smart, always-ahead character he played at the start, he would not have done this. But he is flawed, he is realistic. He lashes out then backs away only to double down then back away equally so, ending in his death. This is where I see many dislike the characterisation of Inseop at the end.
I've seen all too many saying that "Inseop shouldn't kill himself, it's not in character" and that the author must "hate Inseop and only like Gijeong" for ending things this way. While I do not have any connection to the author and can not speak on their behalf, I do not believe they hate the Inseop they created (though the side stories are hurting me physically, please, spare everyone from the character demolition there).
I believe Inseop's love was too much for him to handle, and in his depressed state, he gave up. He could not have Gijeong other than in a physical sense, he could not own her heart, and overtaken by the grief of this realisation, he wept and ended it all.
The ending was flawed. It was rushed. Because of this, character motivations and actions were left muddled. I can understand why others would not agree with his motivations and final choice, but it's frustrating to see just how much some explanations could have done. Had the side stories delved more in the character explanations, even just a message from the author explaining the ending to some degree, I feel the reception of the final chapter would have been better (even slightly, despite how rushed it all was).
I've been typing for an hour all for a manhua. I feel silly. ;;
This is all my opinion, I just wanted a place to put it all out there. Apologies for how drawn out this was, and thank you if you've read it all. ^^