A solution

A story about dustsans in zzz ( short and simple eh )

nah im messing with ya

sans has tried every thing to stop the human from doing more genocide run so he decided he need to be more determined, more LOVE.

After doing his own genocide run, he thought he might had a chance... But he failed, the human memorized his fighting style, his bad habit, and in the end succeeded to kill him, he thought that maybe it is because he haven't reached LV 20 yet, so he do more genocide run, again and again until the human faced him with only LV 1, he thought that maybe this time with the maxed out Lv, he could put this all to an end, but he made one mistake, the human isn't as weak as they were in the first run even with the same Lv and EXP. In one genocide run while waiting for the human at the judgement hall he met an interesting person.

with the information from the mysterious person he then realized that at the end of every genocide run the human offered their own soul to their "partner" which help resetting the world, and each time waking up from that flower bed they became a bit more stronger, knowing that eventually the human will reached the point of overpowering him even at Lv 1, he MADE a choice.

thinking that this is the only and last solution he decided to go to somewhere else, far away with the DT of the monster kind, stopping the human from getting to Lv 20 and reset yet again.

he went back to his house, to his secret lab, looking at the device he then fully concentrate on fixing it, after succeeded on fixing it and activated, sending himself out of this hellhole in the bright light, trapping the demon in the empty underground forever.

waking up in a destroyed town on the surface and travel around, he encountered some monster, but they are different from the monster he knew, they are, more precisely beast than intellectual being

( story may suck since the author is very inexperienced so ya might reconsider spend time for it )