Well, that's some bullshit resolution to keep that problem alive for another time. From the start, the dark lord of destruction was set up as MC's final enemy. Not only because he almost annihilated the Tang clan, but also because he wanted to have his way with MC's mom. And yet, for some reason, the author keeps keeping alive a childhood bully that should have already been dealt with. And what's the motivation behind that bully's grudge? Just that he got put back in his place and hated how weak his actual potential is.
How many alive are currently experiencing the same feelings as that guy? Frankly, his motivations are laughable, and yet some god like demonic ancestor acknowledges that motivation as unique and worth nurturing.