Kingdom Hearts 3D: Dream Drop Distance/Dive to the Heart

After a series of scenes, Riku will begin his final dive. The objective here is to tag 30 Soras, simply by passing through them on your way down. Avoid the Anti-Soras along the way, or attack them for health before they begin their own attacks. Once the ring is open, pass through it and Riku will land on a familiar platform.

Final Boss: Armored Ventus Nightmare
In this battle, Sora is represented by a heart tied to his own. This battle can get a bit chaotic, as the armored foe is constantly changing the arena from white to black and zipping all over the place by dropping into the ground and materializing in front of Riku. Fortunately, his sporadic movements make it easy to catch him off his guard. Lock on to him whenever he materializes again, using ranged attacks when he's far and more suited attacks when he gets too close. As long as you keep a watch on your health gauge, you shouldn't face too much of a struggle here.

When his health bars are taken out, the armored boy moves back for one last showdown with Riku. Press repeatedly to launch a counterattack and defeat the darkness in Sora's heart once and for all.