This is just my personal theory so it could be wrong but I think its all about power dynamics. J is unbeliveably more powerful than Makoto and you can see that he makes the effort to remind Makoto of that fact (like being raped by Fjord, having him collect his father's soul, etc.) I think since J is so powerful, the only way to be on equal standing with him is to destroy him.
I forgot to add that I think Makoto, in his own fucked up way, truly loves J. And like in any relationship, the only true way to feel secure is when both parties are on equal footing. But who knows! Makoto's all fucked up in the head anyways so maybe its not about his love for J LOL
I see. . .thanks u all!!!
Dont really understand. Can someone give me a summary?