Venusaur: Mega Venusaur, G-Max Venusaur
Charizard: Mega Charizards X and Y, G-Max Charizard
Blastoise: Mega Blastoise, G-Max Blastoise
Butterfree: G-Max Butterfree
Beedrill: Mega Beedrill
Pidgeot: Mega Pidgeot
Rattata/Raticate: Alolan Rattata/Raticate
Pikachu: Pichu, G-Max Pikachu, Ash Hat Pikachu
Raichu: Alolan Raichu
Sandshrew/Sandslash: Alolan Sandshrew/Sandslash
Clefairy: Cleffa
Vulpix/Ninetales: Alolan Vulpix/Ninetales
Jigglypuff: Igglybuff
Gloom: Bellossom
Golbat: Crobat
Diglett/Dugtrio: Alolan Diglett/Dugtrio
Meowth: G-Max Meowth, Alolan Meowth, Galarian Meowth
Persian: Alolan Persian
Alakazam: Mega Alakazam
Poliwhirl: Politoed
Machamp: G-Max Machamp
Geodude/Graveler/Golem: Alolan Geodude/Graveler/Golem
Ponyta/Rapidash: Galarian Ponyta/Rapidash
Slowpoke: Galarian Slowpoke, Slowking
Slowbro: Mega Slowbro, Galarian Slowbro
Magneton: Magnezone
Farfetch'd: Galarian Farfetch'd
Grimer/Muk: Alolan Grimer/Muk
Gengar: Mega Gengar, G-Max Gengar
Onix: Steelix
Kingler: G-Max Kingler
Exeggutor: Alolan Exeggutor
Marowak: Alolan Marowak
Hitmonlee/Hitmonchan: Tyrogue, Hitmontop
Lickitung: Lickilicky
Weezing: Galarian Weezing
Rhydon: Rhyperior
Chansey: Blissey, Happiny
Tangela: Tangrowth
Kangaskhan: Mega Kangaskhan
Seadra: Kingdra
Mr. Mime: Galarian Mr. Mime, Mime Jr.
Scyther: Scizor
Jynx: Smoochum
Electabuzz: Elekid, Electivire
Magmar: Magby, Magmortar
Pinsir: Mega Pinsir
Gyarados: Mega Gyarados
Lapras: G-Max Lapras
Eevee: Espeon, Umbreon, Leafeon, Glaceon, Sylveon, G-Max Eevee
Porygon: Porygon2
Aerodactyl: Mega Aerodactyl
Snorlax: Munchlax, G-Max Snorlax
Articuno: Galarian Articuno
Zapdos: Galarian Zapdos
Moltres: Galarian Moltres
Mewtwo: Mega Mewtwo X and Y
If I did not count incorrectly, Kanto Pokemon received 88 forms, evolutions, pre-evolutions, and the other things in your criteria.
Hope I helped!