S Rank

S+

 Xerneas
 Primal Kyogre

S

 Yveltal
 Dusk Mane Necrozma
 Primal Groudon

A Rank

A+

 Zygarde-C
 Mega Gengar
 Marshadow
 Arceus-Ground

A

 Giratina-O
 Arceus-Fairy


A-

 Arceus-Water
 Rayquaza
 Ultra Necrozma
 Ferrothorn
 Ho-Oh
 Mega Metagross
 Lunala
 Gothitelle

B Rank

B+

 Arceus-Dark
 Mega Venusaur
 Arceus-Normal
 Mega Salamence
 Arceus-Flying
 Lugia
 Smeargle
 Mega Lucario
 Mega Sableye
 Tyranitar
 Arceus-Ghost
 Magearna
 Dialga

B

 Mega Diancie
 Blissey
 Celesteela
 Mega Mewtwo Y
 Mega Tyranitar
 Cloyster
 Toxapex
 Deoxys-A
 Giratina
 Mega Gyarados
 Aegislash

B-

 Deoxys-S
 Tapu Koko
 Mega Scizor
 Excadrill
 Naganadel
 Tapu Lele
 Zekrom
 Arceus-Rock
 Arceus-Poison
 Mega Lopunny

C Rank

C+


 Ditto
 Arceus-Ice
 Mega Swampert
 Palkia
 Shuckle
 Arceus-Grass
 Klefki
 Mega Mewtwo X
 Shaymin-S
 Chansey
 Buzzwole
 Mega Slowbro
 Garchomp
 Mamoswine

C

 Mega Blaziken
 Alola Muk
 Kyogre
 Kyurem-W
 Mewtwo
 Landorus
 Dawn Wings Necrozma

C-

 Skarmory
 Arceus-Dragon
 Mega Latias
 Darkrai
 Arceus-Steel
 Hydreigon
 Dugtrio
 Pheromosa

D Rank

If you missed the intro explaining this, D rank is for Pokemon deemed unviable in the Ubers metagame, but are Ubers by tiering. There is no viability ordering on these Pokemon for this reason, so use them at your own risk.

 Arceus-Bug
 Arceus-Electric
 Arceus-Fighting
 Arceus-Fire
 Arceus-Psychic
 Blaziken
 Deoxys
 Deoxys-D
 Genesect
 Groudon
 Mega Kangaskhan
 Reshiram
 Solgaleo