Italics represents newcomers (you would have figured it out anyway, but for completion sake let's state it outright).
Super Mario Bros.
Mario, Luigi, Princess Peach, Bowser, Bowser Jr., Toad
The Big Four (Mario, Luigi, Princess Peach, and Bowser) were all no-brainers, as was cutting Dr. Mario. Then I decided to keep Bowser Jr. due to his prominence in recent and recent-ish
Mario games and due to me genuinely finding his moveset to be fun and inventive. Finally, I decided to throw in a newcomer already and I went with Toad, since I feel that he still is one of the bigger icons of the
Mario series, despite oftentimes being neglected this title. On top of this, I consider the
Mario Kart 64 crew to be the quintessential
Mario group and I want all of them to be included here.
The Legend of Zelda
Link, Zelda, Ganondorf, Champion Link
The Triforce trio is going nowhere, you already knew that. But on top of them I decided to add yet another version of Link and this time, I took full inspiration from the
BotW/TotK duology on the Nintendo Switch. Indeed, I believe that Link should be based on his more classic adventures, while having his unique outing as the Hero of the Wild being fully represented by its own, full-fledged character.
Fire Emblem
Marth, Ike, Chrom, Alear
This might be controversial, since I only kept four swordfighters and I neglected Robin in the process, but I think that Marth, Ike, and Chrom make for a unique enough trio of swordsmen in such a way that nobody will step on somebody else's feet. Newcomer Alear on the other hand feels a bit more Marth-like, but they can add melee attacks to the mix and I'd love to see the Emblems thrown into their moveset to reference Lords and weapons that the aforementioned trio cannot represent.
Pokémon
Pikachu, Jigglypuff, Lucario, Greninja, Tinkaton
Since this is meant to be SSB6, I decided to keep Jigglypuff. I would have loved to have Charizard in its stead, but oh well, it is what it is. Pikachu is a no-brainer and Lucario and Greninja help fleshing out the representation, Generation-wise. Speaking of Generation, from Gen IX I added my favorite 'mon, Tinkaton, which I believe makes for a very good character. I can see her being a very fast character with nonetheless some slow, but incredibly powerful attacks, courtesy of her massive hammer.
2-4 Characters Nintendo Series
Donkey Kong, Diddy Kong, Dixie Kong
Samus, Ridley
Kirby, King Dedede, Meta Knight
Inkling, Octoling
Olimar, Oatchi
Shulk, Pyra/Mythra, Noah
Most of these choices seemed sensible to me: the
Donkey Kong series lost King K. Rool but gained Dixie Kong, so the tradeoff is even imo, then I added Octoling (as their own character, representing
Splatoon 2 and
3), as well as Noah from
Xenoblade Chronicles 3, completing the
Xenoblade trifecta. The most controversial choice is perhaps Oatchi. I'll admit that I needed one newcomer from a series with one character only and it was either him or Tom Nook. In the end, I went with Oatchi because I think it has more to offer. I can see Oatchi having a less strategic moveset than Olimar, using Pikmin mostly as projectiles without the management involved, but taking advantage of his strength as he does in game.
Metroid keeps Samus and Ridley, the two most important characters from the series, and
Kirby is completely unchanged as that trio is so perfect.
Nintendo One-Hit Wonders
Yoshi, Fox, Ness, Captain Falcon, Wario, Villager, Little Mac, Duck Hunt, Andy, Savvy Stylist
The primary goal here was to round up the Original 12, so Yoshi, Fox, Ness, and Captain Falcon were no-brainers. Wario is added due to his importance and to round up the aforementioned
Mario Kart 64 crew, Villager is required imo due to the importance of
Animal Crossing as a series right now and the absence of a clear mascot other than him (
New Horizons put Tom Nook back into the spotlight after Isabelle kind of took his role). Little Mac makes a lot of sense as a bruiser in a fighting game, and Duck Hunt is my choice to represent retro characters altogether (I had to pull a Mufasa on G&W, Ice Climbers, and especially R.O.B.). Newcomers Andy and out-of-field Savvy Stylist complete this heterogenous group, meant to wrap up the Nintendo representation in such a game.
Third Party Characters
Sonic, Bayonetta, Maga Man, Simon Belmont, Cloud, Banjo & Kazooie
The first five characters were quite clear cut: Simon and Mega Man are two icons on the NES, Sonic made arguably the biggest splash of any character in the Smash series, Bayonetta at this point is an honorary Nintendo character and Cloud Strife was another huge addition to the game. For the final slot, PAC-MAN and Banjo & Kazooie grappled until the end, but I chose to go for the bear and the bird, mostly because I think that PAC-MAN perhaps makes a bit more sense as an Assist in its traditional pizza-shaped form. Plus, Banjo & Kazooie too are honoray Nintendo characters.