Not sure if I understood it completely but it seems ahjussi teamed up with the rival to essentially destroy the company. Neck tattoo guy is the boss' son so he had to die too. Killing the boss and the son would mean the company is dissolved which means ahjussi would be freed. Idk what chapter you're in rn so don't read the next paragraph if you're not done with the story yet.
Aaaanyway, the original plan was to kill both boss and son so the rival can take over the company. However, joonie was against it. So ahjussi went back to save neck tattoo guy and helped him defeat the rival ahjussi originally teamed up with. Phew.
Can someone explain to me the whole ordeal about neck tattoo guy and ahjussi beating him up in order to get out of the company??