Dark Samus

Dark Samus is the main antagonist of the Metroid Prime trilogy of the Metroid series. Debuting in Metroid Prime 2: Echoes as a doppelgänger of Samus Aran, Dark Samus is actually the result of the Metroid Prime fusing itself with Samus' Phazon Suit (and a sample of Samus' DNA by extension) following its near-death defeat on Tallon IV in Metroid Prime.

Super Smash Bros. Brawl
In Super Smash Bros. Brawl, Dark Samus appears as both a collectible trophy and a sticker, both of which depict her appearance in Metroid Prime 2: Echoes. In Brawl's Adventure Mode, The 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 Side. Although it is meant to represent Dark Samus herself, this Dark Samus is merely Samus' model recolored entirely 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 scattershot of bullet-like blasts from her Arm Cannon, or a barrage of energy balls that home in on enemies. If enough damage is dealt to Dark Samus, 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' alternate colorations.

Super Smash Bros. Ultimate
Dark Samus is as an unlockable playable character in Super Smash Bros. Ultimate; this marks not only her playable debut in the Super Smash Bros. series, but also her first playable appearance in any game. Due to being an Echo Fighter of Samus, Dark Samus fights almost exactly like Samus, but has a number of different animations and unique taunts and victory poses. Compared to Samus, Dark Samus uses Phazon in her moveset, as indicated by blue flames with an electric effect for all but two of Samus' respective flame-based attacks, and dark blue energy for Charge Shot and Zero Laser. In addition, her rolls involve her evading via levitation instead of transforming into a Morph Ball.

In Ultimate's Adventure Mode, World of Light, 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 and thus enabling her to join Kirby's team against Galeem and Dharkon.

Classic Mode route
Dark Samus' Classic Mode route is titled "The Great Poison Given Form", where she teams up with "dark" versions of characters (in reference to Phazon Corruption) against protagonists.

Super Smash Bros. for Nintendo 3DS / Wii U trophy
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.

amiibo

 * Summoned into the Super Smash Bros.™ Ultimate game, Dark Samus joins the battle as Samus's echo fighter. With floatier movement, she's a little different from Samus--and she doesn't roll when dodging or jumping. If you look closely, you can see that her bombs and missiles look a little different, too.

Name in other languages
Samus Oscura