Echo Fighters for characters first appearing in the original Super Smash Bros. Brawl.
27. Dark Meta Knight
Original Fighter: Meta Knight
Odds: Low
Dark Meta Knight is a copy of Meta Knight's dark side first seen in Kirby & The Amazing Mirror. Like Shadow Kirby, this character is possible but may be too obscure for Super Smash Bros. Ultimate.
Dark Meta Knight has everything needed to be a great Echo Fighter, but I just wouldn't bet on it. Dark Meta Knight could just be a costume for Meta Knight.
Galacta Knight is, arguably, another option for a Meta Knight Echo Fighter, but the odds may be even lower for this pick. Why? A Smash Bros. Ultimate screenshot has been revealed showing off a Galacta Knight costume for Meta Knight complete with a different mask.
36. Dixie Kong
Original Fighter: Diddy Kong
Odds: High
While I'd rather see Dixie Kong introduced as a new unique character, I could also see her coming in as a slightly altered Echo Fighter for Diddy Kong.
Now that King K. Rool has made cut, it's very likely that Sakurai has considered Dixie and how to implement this popular Kong into the game. Sure, her recovery may need to be a hair-spinning version of Donkey Kong's, but it's very likely in my opinion.
38. Shadow
Original Fighter: Sonic
Odds: Very High
Sonic’s Echo is his evil twin from the Adventure games, and we can gleefully ignore his use of firearms in his self-titled 2004 title.
We don’t really have a Sonic villain playable, so including Shadow would make for an easy trip down that road. Possibly the only thing holding him back is that he’s been an assist trophy before. That said, his Assist Trophy has been absent so far in Super Smash Bros. Ultimate.
39. Shadow Dedede
Original Fighter: King Dedede
Odds: Very Low
Like Shadow Kirby, Shadow Dedede is the Mirror World version of King Dedede found in Kirby: Triple Deluxe. However, this odd variant of the King can only be seen as the final boss of the Dededetour bonus mode.
As with all the Kirby Echo Fighters on this list, I just have doubts that they'd make the cut.
40. Louie / Brittany
Original Fighter: Olimar / Alph
Odds: Medium
Louie, Captain Olimar's clumsy coworker, would be a great Echo Fighter for the Pikmin Star. Of course, Olimar's alternate "costume" of Alp would need an ally too which is why I think Brittany from Pikmin 3 would work perfectly as a Louie alternative "costume" of sorts.
It's impossible to get inside Sakurai's head, so we don't know if he'd be open to making Echo Fighters for characters as unique as Olimar, but it's a possibility.
43. Shadow Link
Original Fighter: Toon Link
Odds: Very Low
While this character would work perfectly as an Echo fighter it suffers from a major problem. There are already three Link variants in Super Smash Bros. Ultimate. Additionally, Shadow Link was a Toon Link alternate costume in the previous Smash Bros. game, so it's likely to return as such in Ultimate.
44. Panther
Original Fighter: Wolf
Odds: Low
Panther is a member of the Star Wolf team introduced in Star Fox Assault and could easily steal Wolf's moveset. The guy has claws and can wield a blaster, so it should be simple.
The main thing holding him back is that he is fairly obscure outside the realm of Star Fox fans. Sorry John.