If you're a horror fan, you'll love this AU.
I did some research and the idea to this AU is really creative.

In a nutshell, Frisk has either reset too much or corrupted the game files to make all the characters terrifying monsters.

I like this more than Underfell because it's more creative, even though it makes all of monsters evil. Underfell never explained how everyone became evil.

All the characters are now creepy as frick and have really original designs. Instead of Asgore keeping human souls in glass capsules, he wears six colored hearts around his neck. Whenever you die, instead of taking your soul, they take your heart.

I'd have to give this one a 7/10. It's a really creative AU that appeals to horror fans that enjoy Undertale.