There are three broad categories of Pokemon that could be banned in any given VGC regulation: Mythicals/Event Pokemon, which are always banned; Non-Restricted Legendaries/Paradox Pokemon, which could be banned; and Restricted Legendaries, which are only allowed in a small handful of regulations.
In the current VGC regulation, Regulation H, all of the above are banned, meaning the banlist is as follows:
(Note that I will be including Pokemon not in SV for future reference)
MYTHICALS/EVENT:
Mew
Celebi (Not in SV)
Jirachi
Deoxys
Phione
Manaphy
Darkrai
Shaymin
Arceus
Keldeo
Meloetta
Genesect (Not in SV)
Greninja (Battle Bond)
Diancie
Hoopa (Both forms)
Volcanion
Magearna
Marshadow (Not in SV)
Zeraora (Not in SV)
Meltan (Not in SV)
Melmetal (Not in SV)
Zarude
Pecharunt
LEGENDARY NON-RESTRICTED POKEMON AND PARADOX POKEMON:
Articuno (Both forms)
Zapdos (Both forms)
Moltres (Both forms)
Raikou
Entei
Suicune
Regirock
Regice
Registeel
Latias
Latios
Uxie
Mesprit
Axelf
Heatran
Regigigas
Cresselia
Cobalion
Terrakion
Virizion
Tornadus (Both forms)
Thundurus (Both forms)
Landorus (Both forms)
Tapu Koko (Not in SV)
Tapu Lele (Not in SV)
Tapu Bulu (Not in SV)
Tapu Fini (Not in SV)
Kubfu
Urshifu (Both forms)
Regieleki
Regidrago
Glastrier
Spectrier
Enamorus
Great Tusk
Scream Tail
Brute Bonnet
Flutter Mane
Slither Wing
Sandy Shocks
Iron Treads
Iron Bundle
Iron Hands
Iron Jugulis
Iron Moth
Iron Thorns
Wo-Chien
Chien-Pao
Ting-Lu
Chi-Yu
Roaring Moon
Iron Valiant
Walking Wake
Iron Leaves
Okidogi
Munkidori
Fezandipiti
Ogerpon (All forms)
Gouging Fire
Raging Bolt
Iron Boulder
Iron Crown
RESTRICTED POKEMON:
Mewtwo
Lugia
Ho-Oh
Kyogre
Groudon
Rayquaza
Dialga (Both forms)
Palkia (Both forms)
Giratina (Both forms)
Reshiram
Zekrom
Kyurem (All forms)
Xerneas (Not in SV)
Yveltal (Not in SV)
Zygarde (All forms) (Not in SV)
Cosmog
Cosmoem
Solgaleo
Lunala
Necrozma (All forms)
Zacian (Both forms)
Zamazenta (Both forms)
Eternatus
Calyrex (All forms)
Koraidon
Miraidon
Terapagos
Sources: https://www.serebii.net/scarletviolet/rankedbattle/regulationg.shtml and https://pokemondb.net/scarlet-violet/unobtainable for Pokemon not in SV.
