OKAY HAHAHA yin nezha, that fucker. for all his ideals of duty, and for everything he had done for it, whatever that was, he still cannot kill Rin. He chose her life, time and time again. Even if the very act of choosing her life over her death meant the death of thousands of thousands. yet he still chose it. he knows that she will bring, even unintentionally, death and chaos to everything, and that she did. yet he cannot still kill her.
It was Rin who had to carve the knife to her chest at the end.

















