Dark Samus

Dark Samus is the main antagonist of the Metroid Prime subseries of the Metroid series debuting in Metroid Prime 2: Echoes. She is a doppelgänger of Samus Aran and a form of Metroid Prime, created after it merged with Samus's Phazon Suit to survive following its defeat on Tallon IV in the original Metroid Prime.

Super Smash Bros. Brawl
In Super Smash Bros. Brawl, Dark Samus does not appear in a physical form, though she appears as both a collectible trophy and a sticker, both depicting her appearance in Metroid Prime 2: Echoes. In Subspace Emissary, her sticker can only be equipped by Samus and Zero Suit Samus, and gives them a +11 increase in their battering resistance when equipped.

A "Dark Samus" appears in co-op Event 7: Battle of the Dark Sides, though while it is meant to represent this character, this Dark Samus is merely Samus's model recolored to be completely black.

Super Smash Bros. for Nintendo 3DS / Wii U
Dark Samus appears as an Assist Trophy in Super Smash Bros. for Nintendo 3DS and Super Smash Bros. for Wii U, taking her appearance from Metroid Prime 3: Corruption. She attacks using a variety of Phazon-based abilities, such as tentacles that sprout from the ground, a burst of shots from her arm cannon, or spherical missiles that home in on enemies. If enough damage is dealt to her, a ball of light forms around her before she disappears; otherwise, she simply disappears after a period of time. Dark Samus is also the basis for one of Samus's alternate colorations.

Super Smash Bros. Ultimate
Dark Samus is as an unlockable playable character in Super Smash Bros. Ultimate, which marks not only her playable debut in the Super Smash Bros. series, but also her first playable appearance in any game. Being an Echo Fighter of Samus, Dark Samus has the same moveset, with only minor differences such as electric properties for Arm Cannon-based standard attacks (down tilt, side smash, up smash and forward air attacks). She also floats above the ground in a fashion similar to Mewtwo. Dark Samus's Final Smash, Phazon Laser, is similar to Samus's Zero Laser, though it is colored black rather than blue.

In the Adventure mode, Dark Samus is not seen when the fighters oppose Galeem for the first time. However, she, like every fighter except Kirby, is hit by one of Galeem's beams of light and imprisoned in the World of Light, where a Puppet Fighter of her is created. Said Puppet Fighter initially serves Galeem, but is later brought under Dharkon's control. The Dharkon-serving Dark Samus Puppet Fighter is eventually defeated, freeing the real Dark Samus who joins Kirby's team against Galeem and Dharkon.

Classic Mode route
Dark Samus's Classic Mode route is titled "The Great Poison Given Form", where she teams up with "dark" versions of characters against protagonists.

Trophies
Blue indicates exclusive to the Wii U version.

Palutena's Guidance

 * Palutena: Is that Dark Samus?!
 * Pit: You know her?
 * Palutena: She's a being of pure Phazon created after Metroid Prime absorbed DNA from Samus's Phazon Suit.
 * Pit: No wonder she looks like Samus.
 * Viridi: Samus's suit and a Metroid combined? There's no way she isn't strong.
 * Palutena: Oh, she's strong all right. Along with ruthless and cunning.
 * Pit: Um, so what's a Phazum?
 * Palutena: It's Phazon. A blue radioactive substance that can produce massive amounts of energy. However, it can suddenly mutate and become invasive to mineral elements, making it incredibly dangerous.
 * Viridi: The monkeys never should have messed with the stuff, but they insisted and it blew up in their faces.
 * Palutena: Dark Samus was defeated, but the power of Phazon brought her back. A sentient Phazon being with free will. Between Dark Samus and Ridley, Samus has no shortage of archenemies.

Name in other languages
Samus Oscura