Legendary Tier 1 (Pokémon of great power that may have legends and stories surrounding them, more like legendary catches)
>Articuno, Zapdos, Moltres
>Raikou, Entei, Suicune
>Latias, Latios, Regirock, Regice, Registeel
>Uxie, Mesprit, Azelf, Heatran, Regigigas, Cresselia
>Cobalion, Terrakion, Virizion, Tornadus, Thundurus, Landorus
>Nihilego, Buzzwole, Pheromosa, Xurkitree, Celesteela, Kartana, Guzzlord, Poipole, Naganadel, Stakataka, Blacephalon
Legendary Tier 2 (Pokémon of incredible power that often end up in legends and world lore, catching them is generally not thought of as possible)
>Mewtwo
>Lugia, Ho-Oh
>Kyogre, Groudon, Rayquaza
>Dialga, Palkia, Giratina
>Reshiram, Zekrom, Kyurem
>Xerneas, Yveltal, Zygarde
>Cosmog, Cosmoem, Solgaleo, Lunala, Necrozma
Mythical (extremely rare Pokémon that don't seem to exist in any known habitats, much like cryptids)
>Mew
>Celebi
>Jirachi, Deoxys
>Phione, Manaphy, Darkrai, Shaymin, Arceus
>Victini, Keldeo, Meloetta, Genesect
>Diancie, Hoopa, Volcanion
>Magearna, Marshadow, Zeraora, Meltan, Melmetal