In phase 1, sans starting to mutate and eat all human population and destroying the city, his powers are bones, gaster blaster, and telekinesis, and he never uses a teleportation, he can stalk you every closer and you die, but if you stalk far away you'll be probably a dead body of a human corpse.

If you defeat him, you must grab a explosive weapons and ammo, it weaken him and parasites start to consume, but her slash doesn't work, it decapitated himself, and there's no stopping him....

community by @gabi744 / @gozobriel155 and @Marcel-likes-games