>>11813869I mean, technically. THE Metroid Prime (as in, the Phazon-irradiated Metroid that was the first game's final boss) would become Dark Samus after absorbing her Phazon Suit (and I think DNA?), and a post-credits scene showed the suit mutating and coming to life all bodyhorror-y.
However, we wouldn't actually see Dark Samus's design until Prime 2. Her design would be later refined by Prime 3 as well (this is what Smash Ult's design is based off), but Smash Remix uses her Prime 2 design.