Supernova

Supernova is a Special Move that Mario can use with the power of the final Crystal Star, aptly named the Crystal Star. Both the star and the attack are obtained after defeating Magnus von Grapple 2.0 in Chapter 7. It is the most powerful attack that uses Star Power when the Action Commands are executed correctly. To perform it successfully, the player must rapidly press the button as fast as he or she can. This fills up a small gauge. Once filled, a new gauge appears, but requires faster button pressing to fill. A total of five gauges appear, and each one completed adds 3 hit points of damage to all enemies, piercing defense. If all five gauges are filled, this attack will do 15 damage to all enemies. Using this attack takes six SP.

Trivia

 * On early versions of the game, if the player uses this attack on the Shadow Queen in her invincible form, the game will freeze, possibly because the queen is not supposed to be able to take damage in this state.
 * In real life, a Supernova is the event when a large star dies.