Honestly, the drama started with a good note and story was also interesting until we find out about the ex of ML. Lol, he left her ex just because his brother died. What the hell is this, you were the one who asked your brother to bring the ring not her. So why you should leave her and don't tell he. He left her and started his pathetic life without caring about anyone else. and when he get to know about the SML that he is killer he wanted to get him all the punishment. So what should be your punishment for leaving your gf without any reason. I really don't like the plot twist at the end. Either they should have portrayed the SML as a bad guy from the start or shouldn't have turned him to an evil guy in one go.
The ML lack humanity he only think about himself. I also don't like FL gesture when the SML asked for forgiveness for his brother act and she turned a blind eye like he had murdered the ML little brother.
I think the writer was drunk when writing last episodes. She didn't realized what she wrote in the end.