"That's right, Sora. Your friends are your power. And with that power, you don't need any weapons. The light within your heart gave hope to many people. You've become a part our hearts, and we've become a part of yours. And now, all the lights of our hearts will become one. To make your light even stronger. To create the Ultimate Light."
tldr: Sora used the light within his friends hearts and went super Saiyan
Inspired by this video: https://www.youtube.com/watch?v=KNQ6xnWA5Dg
Credits:
Original Model: http://forums.kc-mm.com/Gallery/BrawlView.php?Number=211966
Normal form animations: Nintendo
Most alternate form animations: http://forums.kc-mm.com/Gallery/BrawlView.php?Number=209667
Kamemaha animation: http://forums.kc-mm.com/Gallery/BrawlView.php?Number=209833
Keyblade attachment in the screenshot is linked below
Update 2-17-24: Added a new version with reduced file size