
Well think of it this way:
- emotionless hunter kills things
- doesn't feel
- meets girl who teaches him how to feel, initially he hurts her
- villain influenced his behaviour in the past, that's why he kills things
- he loves the girl, treats her good, but kills the villain.
Minho is more of a plot point than anything.

It's just as poor as the plot of 50 shades and twilight and BJ Alex but it works for them because they have a male problematic lead. It suddenly doesn't work when the problematic lead is female. (((The point of most of those problematic bl's and love stories (like twilight, 50 shades of gray) is that by the end, the male lead changes by the power of love, thereby insinuating that the rapey, violent behaviour was never ideal and had to change. )))

It's not like these stories didn't face criticism. Look at the newest chapters of BL "Master of master" most people talk about rape and how disappointing the story line is.
Also in no of this stories the victim was so badly humiliated and treated like trash to the veeeery end. (Didn't read or watch 50 shades of gray though and not going to)

Because bj alex ended with Jiwon changing and caring for Donghyun. Sadistic Beauty doesn't exactly do that. If it did, it wouldn't be called out so much. The readers tolerated Duna's rape for so long BECAUSE they were expecting growth. Now you can call them snowflakes, prudes or whatever but it still holds that what Duna did was justified and she had a happy ending when she didn't deserve one after committing so many crimes.

We really did a topic drift. There are people biased in one side and other in the other side. I myself don't care about gender at all. Abuser is an abuser.
The short summary you've posted about the plotline is not really adequate at any point. The main focus of the story is on the villain's and protagonist's relationship, villain isn't just killed, he is tormented through a big part of a story too and that's makes him also a victim,a fact which wasn't recognised at any point of the story. The sweet lover who taught protagonist is not some savior, he is blind follower. In the end we could even argue that protagonist has also negative impact on him judging by the last scenes.
People who appreciate duna's character and have problem with translator's comment are perverts and psychologically challenged.