Instructions
Press the jump button immediately to leap over Wa-Wa's first projectile. Jump forward onto the first floating platform.
Advance past the other two floating platforms by jumping forward onto them. Wa-Wa will shoot low projectiles to impede your progress. Press the jump button when the projectile is near to hop over it.
Jump onto the platform that Wa-Wa is on. Immediately press the special attack button, which causes Crash to perform the Spin Crash attack. This move will hurt Wa-Wa considerably, and cause him to teleport to another platform.
Repeat the process from Steps 2 and 3 to reach Wa-Wa again. This time, he will release a fire projectile in addition to the other one. Press down on the directional pad to crouch and avoid the fire. Jump on the platforms until you reach Wa-Wa and hit him with the Spin Crash.
Follow the same set of instructions from Steps 1 through 4 to reach Wa-Wa again. Attack him with the Spin Crash attack to finally defeat him. As a prize, you receive the Double Jump special attack, allowing you to leap twice as high.