Stealing stuff and mass murdering people doesn't seem like a good comparison.
You are missing my point. They both started out the same way, but their trauma showed itself differently. Yes, killing someone is bad, (also I HIGHLY doubt that Sangwoo has mass murdered unless I’m missing the time he planted a bomb in a public place or started a pandemic), but it isn’t Sangwoo’s fault that he is doing this, just like it isn’t Bum’s fault that he is stalking people, not to mention Bum has killed someone too now -yes it was half forced, yet still, he doesn’t show proper remorse at all, more like worry that he’ll get caught-.
The fact that Sangwoo’s crime is bigger is blinding people to the fact that Sangwoo is also someone who is doing this because of abuse he has received as a kid, and just because we see more of Bum being abused, doesn’t mean Sangwoo hasn’t had the same problems or worse.
If anything, Sangwoo has been abused much more in his childhood to become the way he is.