Does not account for taunts, victory animations, and the simple "this move now deals less damage" stuff you'd see in balance patches. Made within the context of a casual game.
Mario:
-Happier disposition
-Cape is swapped for tanooki tail. Functionally the same
-Mario Tornado has been restored, now with Cappy floating around as a disjoint. Mario himself is a sweetspot however, so Cappy functions as a damageless get-away tool like FLUDD
-Dash attack is the SM64 tackle
Donkey Kong:
-Happier disposition
-Classic Voice
-Headbutt involves DK slamming a barrel. Functionally the same.
-Down Smash and Down B’s animations are swapped - the new Down Smash can still be held as it could be as a special when less than half charged. Down B shares a charging resource with Giant Punch.
-Konga Beat is back
Link
-Skyward Sword/MK8 design.
-Classic bomb and hook shot restored
-Jab laser removed.
-New Final Smash: Heroes Across Time - TP, BOTW, and OOT Link assist as spirits.
Samus
-Some moves have ice properties. Purely cosmetic
-ZSS stance change restored to Final Smash.
Dark Samus
-Smash Attacks are now disjoints, with the assist trophy attack being used as a D-Smash.
-Laser homes and missile goes straight forwards
Yoshi
-Horse-like posture restored
-New Final Smash: Super Happy Tree - Yoshi eats fruit from the Super Happy Tree and his health is changed to -200%
Kirby
-Slide kick down tilt
-Air movement is closer to Jigglypuff
-Chef Kirby restored as Final Smash
-Some copy moves are side, up, or down specials
-Can get a random copy with an uninterrupted taunt
-Some copies aesthetically redesigned, such as Peach having a wig
Fox
-Shine restored to Melee functionality
-Landmaster restored as Final Smash
Pikachu
-Unmodified
Luigi
-Negative Zone restored
-Poltergust removed from grabs
-RNG powerful variants added to Luigi Tornado and Fireball - Fireball’s RNG variant summons a ghost who drags anyone in its path, while Tornado’s goes to the maximum height automatically
Ness
-PK Fire now has a use meter. Like wonderwing, it cannot be recharged unless you’re KO’d.
-New Final Smash: PSI Rockin’. Similar to Shadow Mario Paint. Jeff is involved.
-Smash 64 kick nair restored
Captain Falcon
-Unmodified
Jigglypuff
-Unmodified
Peach
-Peach Bomber rethemed to P-Wing
-Forward tilt is Peach creating magic sparkles with her hand, a la Fantasia Mickey
-Back air no longer has heart effect
-Toad replaced with Toadette for default costume, all other costumes have different-coloured male Toads.
Daisy
-All changes to Peach apply to Daisy
-Toad replaced with Gao, who breathes fire.
-Turnip replaced with carrot
Bowser
-Goofier disposition
-Proper voice
-Melee run animation implemented as dodge animation
-Goes into shell for crouch.
-Down B and down air animations swapped, Down B turns Bowser blue to reference the Blue Shell and ends with a cosmetic explosion.
-New Final Smash: Fury Bowser. Functionally the same as Brawl Giga Bowser
Ice Climbers
-Nana now purely copies Popo’s actions instead of being a unique CPU that follows.
Sheik
-OOT Design
Zelda
-TP Design and associated personality (Ultimate FS kept)
Dr. Mario
-Represents Dr. Mario as a series instead of Mario.
-No changes made to Mario apply to Dr.
-Angst and anger increased slightly
Pichu
-New Final Smash: My Pokemon Ranch - sends a foe into My Pokemon Ranch, where they are greeted by many playful Pichus, who accidentally zap them. Each character gets a Pokemon Ranch model
-Sleeping crouch restored
Falco
-Restored to Melee iteration completely
-Arwing is still FS, but controllable instead of cutscene
Marth
-Unchanged
Lucina
-Has tipper, now a full Marth clone.
Young Link
-Unchanged
Ganondorf:
-Has float
Mewtwo:
-Unchanged
Roy
-Unchanged
Chrom
-Unchanged
Mr. Game & Watch
-Down throw is based on Mario’s Cement Factory, with G&W turning a foe into cement; forward throw is Donkey Kong Hockey with G&W turning into DK; up throw is based on Egg, with the wolf throwing a foe up and down using his basket; back throw is unchanged.
-Changes forms for all moves, even Mario character moves
-New jab: turning into Link from Zelda and slashing
-Stanley is now F-Smash
Meta Knight
-Unchanged
Pit
-Unchanged
Dark Pit
-Unchanged
Zero Suit Samus
-Down throw sped up.
-Stance swap implemented in Final Smash
Wario
-Wario-Man FS from Brawl restored
-Down throw is a shoulder drop
-Animation has more gross-out
-Down Smash has Wario propelled by his farts
-Down air is a ground pound stall and fall, with a fart.
-Forward Smash and down tilt have Wario pick a visibly-rendered booger before doing so.
-Fart meter is signified by a visible fog coming out of Wario’s butt
-Wario burps when releasing foes from chomp
Snake
-Brawl FS restored
Ike
-Unchanged
Pokemon Trainer
-Pokemon doesn’t swap when KO’d
-Charizard Rock Smash implemented as side smash
-Can press back + down B to swap to the other Pokemon
-New Final Smash, now features a random selection from 6 of the original 151 Pokemon alongside the trainer 3. All original 151, including Jigglypuff and Pikachu, are featured. Also uses GB text instead of 3DS
Diddy Kong
-Canon voice
Lucas
-Duster added to Final Smash
Sonic
-Complete moveset revamp
-Uses classic design with Greg Martin mohawk.
King Dedede
-Brawl Final Smash restored
-Waddle Dee Toss restored
Olimar
-Has a voice
Lucario
-Takes small recoil damage in some moves.
ROB
-Stack-Up directional voice clips used for throws
-Hector in background like Pokemon Trainer
Toon Link
-Unchanged
Wolf
-Has landmaster
Villager
-Unchanged
Mega Man
-Completely reworked
Wii Fit Trainer
-Unchanged
Rosalina & Luma
-Luma colour is based on alt
Little Mac
-Significantly better air fighter
Greninja
-Unchanged
Miis
-Unchanged
Palutena
-Heavenly Light implemented as Up Smash, still deals no knockback.
Pac-Man
-Butt-Bash down air, using the pizza transformation
-Down Smash summons Pooka & Fygar, Up Smash summons Gyaraga, and side smash summons Mappy.
-Turns into US cabinet art design for Up B
Robin
-Meter removed completely
Shulk
-Future Connected design by default
Bowser Jr.
-Unchanged
Duck Hunt
-Mr. Stevenson and Tin Star added as extra rare Wild Gunman, both most and equally powerful.
-Can becomes weaker with every shot.
Ryu
-Input commands removed
-1v1 directional removed
Ken
-Input commands removed
-1v1 directional removed
Cloud
-Limit can only charge from Down B
Corrin
-Unchanged
Bayonetta
-Unchanged
Inkling
-Unchanged
Ridley
-Bigger
Simon
-Completely reworked
Richter
-Clone of the new Simon
King K. Rool
-Unchanged
Isabelle
-Unchanged
Incineroar
-Unchanged
Piranha Plant
-Unchanged
Joker
-Arsene charges from attacking instead of being attacked, teammate charge is still comeback based.
Hero
-Command Selection replaced with Snooze
-Erdrick is default
-Critical Hits reworked: instead of RNG, they appear only on Smash Attacks if performed out of a long combo.
Banjo & Kazooie:
-Given Nuts & Bolts design as default to better represent Xbox
-Uses the Mumbo Wrench in forward tilt.
-Throws are all Mumbo Wrench based. No tether grab however.
-New Final Smash: Bolt Bucket. Nuts & Bolts inspired, with a car ramming into foes.
Terry
-Command inputs removed
-1v1 directional removed
Byleth
-Unchanged
Min Min
-Completely reworked
Steve
-Completely reworked
Sephiroth
-Unchanged
Pyra/Mythra
-Has a brand new Smash-specific design, similar to Pit.
Kazuya
-Completely reworked
Sora
-Unchanged