My last Mushroom is the first one. The one in The World that Never Was. Any help?

 

There ya go lol

I used Wisdom form, negative combos, and I stuck to the beat (no pun on IX, just try to feel the rhythm)

Oh...that mushroom

Got i!

Final Form, then when the mushroom reverses first wait for it to finish then the right timing you press triangle then he would not see youthen start attacking him as many times as you can keep doing it then you defeat it.

Add some points strategy from SorRik, you can use Fenrir (for negative combo) and make sure you press triangle at Second Reaction Command (Sora will stand behind the mushroom), and attack the mushroom.