Echo Fighters for characters first appearing in the original Super Smash Bros. Ultimate.
64. Octoling
Original Fighter: Inkling
Odds: Very High (DLC)
Octolings have been gaining popularity as this year it became possible to play as them in Splatoon 2's Octo Expansion DLC. Guys, they are taking over!
Splatoon is a very popular game and I feel like adding Octolings wouldn't be too difficult considering they use similar weapons as Inklings. A few standard Echo Fighter changes would need to be made.
That said, Super Smash Bros. Ultimate started development before Octolings became a bigger part of the Splatoon universe, so we may only see this character if or when DLC starts hitting Super Smash Bros. Ultimate.
66. Meta Ridley
Original Fighter: Ridley
Odds: Very Low
Meta Ridley is Ridley after Samus had defeated him in her original adventure. However, now he has been enhanced with cybernetic parts by the Space Pirates to compensate for his injuries.
Fans of the Metroid Prime series will remember Meta Ridley as he is one of the major bosses. While unlikely, maybe his Final Smash could see him morphing into the Phazon corrupted Omega Ridley for the duration of the animation.
I don't think Meta Ridley will make the cut, especially since we've seen what looks to be a Meta Ridley costume for Ridley in Smash Bros. Ultimate. But who knows, maybe it's a master level Sakurai troll.