ML is basically a serial killer (but not really).

His first kill was his Abusive Dad who used drugs. He chopped his dad's body into 37 pieces to frame his neighbour, Ji Shiming (?), who is a famous serial killer who cuts up the bodies of his victims and ties the dismembered pieces with red ropes. The ML successfully framed Ji Shiming (?) although this was his first mu*der. According to the police in the novel, the body was cut up perfectly and it looked as if it was done by someone with great skill and experience. Only MC and ML know that it was done by a 7yo.

His second & third kill was performed at age 17 I believe (I'm confused who he killed when lol) He killed a mu*derer who set his eyes on MC. A side character, Yan Wenbai (?) witnessed the mu*derer killing his victim, and to not get caught he pushed the MC into the limelight and escaped. MC told ML this and YWB was hospitalised later due to the MLs planning. The MC was totally clueless that a mu*derer was tailing him btw, the ML killed the mu*der and realized the mu*derer had an accomplice and killed the accomplice too.

The MLs 4th, 5th, 6th & 7th kills were his loan sharks. His loan sharks threatened to do stuff to MC if ML didn't pay back his debt, ML tampered with the car they were in and they died in a car accident (they were drunk too). He killed all 4 in one go.

The MLs 8th, 9th, 10th & 11th kills were none other than MCs bosses who were planning to drug and r!pe MC. They wanted to use 4 drugs and only used 2 when ML caught them, took MC to the hospital, and got him treated. The ML used those drugs later to kill all 4 of them and took over their company. (ML was 24 when these kills occurred I believe)

And it is said that ML is indirectly responsible for 2 more deaths, I'm not too sure about them as I don't remember. But ML tricked the mu*derer (his 2nd kill) into thinking that Yan Wenbai was infact MC. The mu*derer went after YWB and found out it wasn't MC, but it was too late, he couldn't let YBW escape. So the mu*derer pushed YBW onto incoming traffic and YBW was hit by a car and is hospitalized and suffers from mental trauma.

His parents are tiger parents: very strict, controlling and annoying. They or mostly his mom expects nothing but perfection from him. His mom was lowkey (mentally) abusing her child and it was very obvious that MC hated his family situation. He mentioned multiple times how boring and monotonous his life was until he met ML. How he hated his parents fake demeanor and etc. So for the author to put a heavy emphasis on that only to completely ignore this later on was very disappointing and unexpected. Or maybe I just completely missed it due to mtl-ing the story but as far as I know the MC is still in contact with his mom.