Pathfinder 1st Edition Class Tiers

Tier 0: Nothing (no published class is this powerful, but they can be with certain builds like a practical painter wizard)

Tier 0.5: Sorcerer (Razmiran Priest)

Tier 1: Arcanist, Cleric, Druid, Wizard, 

Tier 1.5: Bard (w/ Music Beyond the Spheres), Oracle (Spirit Guide, w/ Dreamed Secrets, Ancient Lorekeeper), Psychic (w/ Mnemonic Esoterica), Shaman, Skald (w/ Music Beyond the Spheres), Summoner (Blood Summoner), Witch

Tier 2: Oracle, Sorcerer, Summoner

Tier 2.5: Inquisitor (Monster Tactician), Psychic, Stalker

Tier 3: Alchemist, Antipaladin (Fiendish Bond w/ succubus or shadow demon), Bloodrager (Urban), Inquisitor, Investigator, Magus (Bladebound, Eldritch Archer, Hexcrafter), Mesmerist, Occultist, Paladin (Sacred Servant + Oath of Vengeance), Omdura, Rogue (Eldritch Scoundrel), Skald, Unchained Summoner, Vigilante (w/ spellcasting), Warpriest

Tier 3.5: Antipaladin, Bard, Barbarian (most archetypes), Bloodrager, Brawler (most archetypes), Hunter, Magus, Medium, Paladin, Spiritualist, Striker

Tier 4: Adept, Barbarian, Brawler, Fighter (Martial Master, Mutation Warrior), Monk (Monk of the Lotus, Qinggong Monk), Ranger, Rogue (True Professional), Unchained Barbarian, Unchained Monk, Unchained Rogue, Vampire Hunter, Vigilante

Tier 4.5: Fighter, Kineticist, Shifter, Slayer, Monk, Ninja, Rogue

Tier 5: Cavalier, Gunslinger, Samurai, Swashbuckler

Tier 5.5: Expert

Tier 6: Aristocrat, Commoner, Warrior

Others: Gentleman (the class is satirical / intentionally unplayable)