AAA Ubers Viability Rankings (Pokemon within ranks are ordered in viability too)

S Rank
Xerneas (Tinted Lens, Dazzling, Turboblaze)
Necrozma-Ultra (from Dawn Wings: Psychic Surge, Magnet Pull)

A+ Rank
Yveltal (Triage, Regenerator)
Marshadow (Tough Claws, Magic Guard)
Mewtwo (Sheer Force, Psychic Surge)

A Rank
Rayquaza (Aerilate)
Giratina (Poison Heal, Regenerator)
Arceus (Pixilate, Poison Heal, Scrappy, Tough Claws, Guts, Magic Bounce, Defiant)

A- Rank
Kyogre (Primordial Sea)
Lunala (Adaptability)
Solgaleo (Unaware, Regenerator, Flash Fire)
Magearna (Regenerator, Prankster)
Ho-Oh (Magic Guard, Volt Absorb)
Primal Groudon (from Groudon: Grassy Surge, Misty Surge, Intimidate, Download)
Deoxys-Attack (Psychic Surge)

B+ Rank
Arceus-Ground (Multitype)
Mega Mewtwo-Y (from Mewtwo: Psychic Surge)
Blaziken-Mega (from Blaziken: Magnet Pull)
Darkrai (No Guard, Mega Launcher)
Zekrom (Surge Surfer)
Palkia (Adaptability, Swift Swim, Primordial Sea)
Slaking (Poison Heal, Tough Claws)
Arceus-Fairy (Multitype)
Gengar-Mega (Download)
Zygarde-Complete (Power Construct)
Kyurem-White (Sheer Force, Tinted Lens)
Pheromosa (Dazzling, Tough Claws)
Reshiram (Adaptability, Sheer Force, Chlorophyll)

B Rank
Skarmory (Intimidate, Flash Fire)
Jirachi (Unaware)
Celesteela (Volt Absorb, Flash Fire, Prankster)
Heatran (Levitate, Regenerator)
Chansey (Unaware, Magic Bounce)
Regigigas (Poison Heal)
Necrozma-Dawn-Wings (Psychic Surge, Adaptability, Sheer Force)
Kartana (Steelworker)


B- Rank
Kyogre-Primal (from Kyogre: Electric Surge, Download)
Kyurem-Black (Refrigerate)
Groudon (Magnet Pull, Prankster, Mold Breaker)
Deoxys-Speed (Mold Breaker, Magic Bounce)
Shuckle (Prankster, Mold Breaker, Magic Bounce)


C+ Rank
Blissey (Unaware, Magic Bounce)
Lugia (Magic Bounce, Unaware, Poison Heal, Shadow Shield)
Dialga (Regenerator, Levitate)


C Rank
Zygarde (Adaptability)
Blacephalon (Magic Guard, Adaptability)

C- Rank
Xurkitree (Surge Surfer, Sheer Force, Prankster)
Naganadel (Sheer Force)
Shaymin-Sky (Adaptability)

D Rank
Buzzwole (Triage)