Random Ideas I came up with during Robotics club... They kinda suck but oh well (if they already exist tell meh please).
[Consequencetale/UnderSin/Underdust] Everyone is made out of dust, and every time they are spared they die, so whether or not you spare them doesn’t matter: they will still die, and this forces the human to do yet another genocide run (no matter how much Frisk tries to have peace and spare monsters). No matter how much Frisk tries to explain, the monsters can only see the human going genocide on purpose and are scared of them, so basically this AU is a forced genocide run. Also, attacks do little to no damage (the only one who can actually do damage is Sans).
Sans is actually the strongest enemy.
Undyne and Sans, in addition, have massive ‘critical scar/slashes’ on their bodies.
Undyne is in her genocide form, and appears more ‘melted’ than ‘dusty’.
CLOSEST AU(s): Help_tale, Aftertale.