In this event, you can choose any character. You have 3 stock and start with 130% damage, and the same goes for your opponent Samus. When you reappear after losing a stock, you still have 130% damage. You fight on Brinstar.
Just smash her with strong attacks. Smash attacks, Captain Falcon's Knee Smash (Forward A in Air), and Ganondorf's Gerudo Dragon (Forward B) are good attacks to use. Rest (Jigglypuff) is also a good option.
Simply use up-Smash until you win.