From SmashWiki, the Super Smash Bros. wiki
Galactic Avenger is a single-player event match in Super Smash Bros. for Wii U. It takes place on Pyrosphere, and the player controls Samus, and must defeat Samus in her dark color scheme and Ridley in a 150 HP battle. Dark Samus has 180 HP on Hard difficulty. If the player is wearing the dark palette, the computer-controlled Samus will be wearing the default Varia Suit.
This event is unlocked by clearing Identity Crisis. Completing the event does not unlock any further paths.
Completing the event on normal or hard difficulty within 80 seconds awards a Meteor Master Suit equipment.