In the novel he still ends up w the og ml (haeyoung? Forgot his name not worth remembering anyway...), cause mc committed suicide but unfortunately survived and had amnesia or smth and haeyoung took advantage of that, basically "im ur lover pls remember me" type stuff, and so they live happily ever after
Erm clearly you've not read the novel.
ML takes revenge himself on Hyun-woo (making him homeless in a different country with no way of contacting his home)
MC attempts suicide in order to get revenge in front of ML and Taegyeom, but does not go amnesiac, he goes into hiding for a year or so. When Haeyoung finds him by pure chance, he notices he has severe panic attacks (seeing it in action and the people who took care of MC), and he starts pursuing him bit by bit, even taking care of people who took care of MC while he was in hiding.
It's actually Haeyoung who is sick (hallucinates with mc and attempts suicide once in front mc and other goes on rampage trying to follow hallucination mc into the sea and Haewon almost kills both of them, but Haeyoung saves themselves)
That is when MC starts giving ML a second chance, because even though they have been through hell, they are both mentally and physicially in need of the other
ML then helps MC with his recovery and puts him to work too, which is what gives the happy ending, because they both heal with time, TOGETHER. ;)

Just tell me if he gets revenge please, just spoil it for me, cause if he aint gonna chop them up or something im out