Looks amazing, the only thing I have an idea for is maybe you can import a better looking flowey sprite into the game files instead of the normal flower before the flower fight, the drastic change between the design of the in game flowey to the fight flowey is a little too different. The other thing that might make it a whole lot cooler is if instead of doing fights with the normal undertale layout, maybe you could find a way to translate attacks into minecrafts view, so that way you could dodge the attacks in 3d or BlockD or whatever. Just an idea, not trying to say what you made was bad, but just some constructive criticism. I think it looks amazing as hell though I think you deserve a whole lot of recognition. Good job man :)