The powerup can be very useful at most points in the game.
Super Sword is a power-up that was introduced in Super Mario Frenzy. Collecting the power-up will turn the player into their Sword Form. A stronger variant of this power-up, the Hero’s Sword first appears in the first bonus level, unlocked by collecting all Diamond Fragments, it also comes with a shield.
Use Y to do the slice attack and X to do the stab attack. If you have the Hero’s Sword, press ZL to block with the shield, if Motion Controls are on, release ZL and flick the Joy-con to do a surprise attack.