Not really. What purpose would their murders at this point serve to the plot, it would mean they would essentially be handing themselves over to the police, as there was recording of the women and the MC's journey route from the supermarket to the Cabin, and the Cabin is rented tourist accommodation, not Sangwoo's house which is fairy isolated. Instead we saw the psychological drama element of the plot. Bum not knowing how to react to this impulsive Sangwoo who is starting to divulge their secrets, whereas Sangwoo is more concerned with staying with Bum, and having Bum's priority. Bum is empowered now to question Sangwoo about his behaviour and is apparently taking an almost parent like role within their relationship. The bath scene, Sangwoo ducking his head under the water (like a ceremony/ like a baptism/ like a cleansing experience) in order to move the conversation on, so avoidance, when Bum started to question why Sangwoo was behaving impulsively when it could be to the detriment of them both.
Sangwoo has showed that he's being messy about him killing.
Leaving proofs, talking about what he does out loud and joking about it to people since they seem to possess a IQ below your average human, for whatever reason.
It's not about him "having a low IQ" (IQ is contested anyway so isn't really appropriate), it's showing his impulsive behaviour. This could be for a variety of reasons, but if you want to put on your armchair psychologist hat, then it's quite a common symptom of personality disorders. Sangwoo's intelligence isn't relevant, he appears otherwise a competent man, at university and holding down jobs. That still doesn't mean he can't exhibit impulsive, innapropriate or self destructive behaviour.
I don't mean Sangwoo, but the irrelevant characters.
Literally all of them either ignore and go on what Sangwoo just shouted about what he did or laugh about it and how funny "breaking someone's legs" is.
Sorry my mistake. The context being that they were all drunk, and the women probably thought he was just saying absurd things in order to get attention. The only person who doesn't take things at face value was the sacked detective who is obsessing over Sangwoo & Bum, but obviously went about things in the wrong way, such as stalking them, breaking into Sangwoo's house, entering his house without a warrant and being physically violent towards Sangwoo which led to him losing his position. I think maybe the sacked detective might start to play a larger role again, as he seeks some vigilante justice.
Am I the only one worried Sangwoo is going to kill the girl who flirted with Bum? He was all smiles in polite company, but immediately went to rude when the girl said Bum was her type. And while he was openly bragging about his crimes, they seemed more directed at getting the girl to back off from his "wife." He was even openly groping Bum in front of them as he listed reasons why they wouldn't want him, as if to not only scare them off and reinforce to Bum that no one but Sangwoo will accept him, but also to reassure himself that Bum belongs to him. Then he's all like "Baby, don't pay attention to her. I'm so much better than her", straight up tells the girl to fuck off and kicks them out. he's killed for lesser offenses.