Under-termined ( Undertale AU )

Well guys I had another random thought for an AU. This time it’s an Undertale AU I like to call Under-termined  ( Sorry for the pun name I couldn’t help myself. )

In this AU by the time Frisk falls into the underground They suffered so much physical, emotional, and mental abuse that They’ve lost all their determination  and can’t feel anything anymore so their soul is weakened to the point it’s starting to break. With their soul in that condition it’s not strong enough to be used to break the barrier so the monsters come together to try to make them whole again so their soul can be used. But once they become whole and the monsters have given them their own traits can they really kill the child they all nurtured and helped to grow?