Counter is learned by 46 species by level, 46 by machine, 151 by tutor and 88 by egg

Effect, in PokéAPI's words

“Inflicts twice the damage the user received from the last physical hit it took.”

Who learns it

220 species in all, 8 of 24 games shown

Scarlet and Violet: 105 species

Species	Method	Level
Annihilape	Level up	1
Riolu	Level up	12
Lucario	Level up	12
Breloom	Level up	22
Tarountula	Level up	22
Mudbray	Level up	24
Mudsdale	Level up	24
Spidops	Level up	24
Heracross	Level up	25
Scorbunny	Level up	28
Chewtle	Level up	28
Slakoth	Level up	30
Skwovet	Level up	30
Drednaw	Level up	30
Okidogi	Level up	32
Vigoroth	Level up	33
Slaking	Level up	33
Greedent	Level up	34
Iron Boulder	Level up	35
Raboot	Level up	36
Cinderace	Level up	38
Hitmonchan	Level up, Egg	40
Sudowoodo	Level up	40
Hitmontop	Level up, Egg	40
Bonsly	Level up	40
Meditite	Level up	44
Kubfu	Level up	44
Urshifu	Level up	44
Medicham	Level up	53
Falinks	Level up	60
Koraidon	Level up	70
Charmander	Egg
Charmeleon	Egg
Charizard	Egg
Sandshrew	Egg
Sandslash	Egg
Mankey	Egg
Hitmonlee	Egg
Rhyhorn	Egg
Rhydon	Egg
Scyther	Egg
Snorlax	Egg
Chikorita	Egg
Bayleef	Egg
Meganium	Egg
Totodile	Egg
Croconaw	Egg
Feraligatr	Egg
Aipom	Egg
Wooper	Egg
Pineco	Egg
Gligar	Egg
Snubbull	Egg
Granbull	Egg
Sneasel	Egg
Teddiursa	Egg
Delibird	Egg
Houndour	Egg
Phanpy	Egg
Tyrogue	Egg
Torchic	Egg
Combusken	Egg
Blaziken	Egg
Mudkip	Egg
Marshtomp	Egg
Swampert	Egg
Lotad	Egg
Lombre	Egg
Ludicolo	Egg
Makuhita	Egg
Volbeat	Egg
Cacnea	Egg
Zangoose	Egg
Chimchar	Egg
Monferno	Egg
Infernape	Egg
Shieldon	Egg
Bastiodon	Egg
Shellos	Egg
Ambipom	Egg
Munchlax	Egg
Croagunk	Egg
Rhyperior	Egg
Gliscor	Egg
Timburr	Egg
Gurdurr	Egg
Conkeldurr	Egg
Sandile	Egg
Scraggy	Egg
Scrafty	Egg
Zorua	Egg
Axew	Egg
Froakie	Egg
Frogadier	Egg
Greninja	Egg
Goomy	Egg
Passimian	Egg
Jangmo-o	Egg
Hakamo-o	Egg
Kommo-o	Egg
Quaquaval	Egg
Nymble	Egg
Finizen	Egg
Tatsugiri	Egg
Ogerpon	Egg

Brilliant Diamond and Shining Pearl: 52 species

Species	Method	Level
Wobbuffet	Level up	Evolve, 1
Wynaut	Level up	1
Riolu	Level up	12
Lucario	Level up	12
Breloom	Level up	22
Heracross	Level up	25
Slakoth	Level up	30
Vigoroth	Level up	33
Slaking	Level up	33
Hitmonchan	Level up	40
Sudowoodo	Level up	40
Hitmontop	Level up	40
Bonsly	Level up	40
Meditite	Level up	44
Medicham	Level up	53
Charmander	Egg
Rattata	Egg
Sandshrew	Egg
Nidoran♀	Egg
Nidoran♂	Egg
Paras	Egg
Mankey	Egg
Machop	Egg
Rhyhorn	Egg
Chansey	Egg
Kangaskhan	Egg
Scyther	Egg
Snorlax	Egg
Chikorita	Egg
Ledyba	Egg
Aipom	Egg
Wooper	Egg
Pineco	Egg
Gligar	Egg
Sneasel	Egg
Teddiursa	Egg
Delibird	Egg
Houndour	Egg
Phanpy	Egg
Tyrogue	Egg
Torchic	Egg
Mudkip	Egg
Lotad	Egg
Makuhita	Egg
Cacnea	Egg
Zangoose	Egg
Chimchar	Egg
Shieldon	Egg
Shellos	Egg
Happiny	Egg
Munchlax	Egg
Croagunk	Egg

Sword and Shield: 56 species

Species	Method	Level
Wobbuffet	Level up	Evolve, 1
Wynaut	Level up	1
Marshadow	Level up	1
Riolu	Level up	12
Lucario	Level up	12
Pyukumuku	Level up	20
Mudbray	Level up	24
Mudsdale	Level up	24
Heracross	Level up	25
Scorbunny	Level up	28
Chewtle	Level up	28
Skwovet	Level up	30
Drednaw	Level up	30
Greedent	Level up	34
Raboot	Level up	36
Cinderace	Level up	38
Hitmonchan	Level up	40
Sudowoodo	Level up	40
Hitmontop	Level up	40
Bonsly	Level up	40
Sawk	Level up	40
Obstagoon	Level up	42
Kubfu	Level up	44
Urshifu	Level up	44
Buzzwole	Level up	55
Falinks	Level up	60
Charmander	Egg
Sandshrew	Egg
Nidoran♀	Egg
Nidoran♂	Egg
Machop	Egg
Rhyhorn	Egg
Kangaskhan	Egg
Scyther	Egg
Snorlax	Egg
Wooper	Egg
Sneasel	Egg
Delibird	Egg
Tyrogue	Egg
Torchic	Egg
Mudkip	Egg
Lotad	Egg
Shellos	Egg
Munchlax	Egg
Croagunk	Egg
Timburr	Egg
Sandile	Egg
Dwebble	Egg
Scraggy	Egg
Zorua	Egg
Karrablast	Egg
Axew	Egg
Goomy	Egg
Passimian	Egg
Jangmo-o	Egg
Wooloo	Egg

Let's Go Pikachu and Let's Go Eevee: 9 species

Species	Method	Level
Charizard	Level up	1
Raticate	Level up	1
Sandslash	Level up	1
Nidoqueen	Level up	1
Nidoking	Level up	1
Primeape	Level up	1
Machamp	Level up	1
Rhydon	Level up	1
Hitmonchan	Level up	45

Ultra Sun and Ultra Moon: 67 species

Species	Method	Level
Hitmonchan	Level up	1, 61
Wobbuffet	Level up	1
Marshadow	Level up	1
Riolu	Level up	6
Lucario	Level up	6
Sawk	Level up	13
Wynaut	Level up	15
Pyukumuku	Level up	17
Heracross	Level up	19
Breloom	Level up	22
Hitmontop	Level up	28
Slakoth	Level up	30
Vigoroth	Level up	33
Slaking	Level up	33
Sudowoodo	Level up	36
Bonsly	Level up	36
Mudbray	Level up	36
Mudsdale	Level up	42
Buzzwole	Level up	43
Meditite	Level up	44
Medicham	Level up	53
Charmander	Egg
Rattata	Egg
Sandshrew	Egg
Nidoran♀	Egg
Nidoran♂	Egg
Paras	Egg
Mankey	Egg
Machop	Egg
Rhyhorn	Egg
Chansey	Egg
Kangaskhan	Egg
Scyther	Egg
Snorlax	Egg
Chikorita	Egg
Ledyba	Egg
Aipom	Egg
Wooper	Egg
Pineco	Egg
Gligar	Egg
Sneasel	Egg
Teddiursa	Egg
Delibird	Egg
Houndour	Egg
Phanpy	Egg
Tyrogue	Egg
Torchic	Egg
Mudkip	Egg
Lotad	Egg
Makuhita	Egg
Cacnea	Egg
Zangoose	Egg
Chimchar	Egg
Shieldon	Egg
Shellos	Egg
Happiny	Egg
Munchlax	Egg
Croagunk	Egg
Timburr	Egg
Sandile	Egg
Dwebble	Egg
Scraggy	Egg
Zorua	Egg
Karrablast	Egg
Axew	Egg
Goomy	Egg
Jangmo-o	Egg

Sun and Moon: 65 species

Species	Method	Level
Hitmonchan	Level up	1, 61
Wobbuffet	Level up	1
Marshadow	Level up	1
Riolu	Level up	6
Lucario	Level up	6
Sawk	Level up	13
Wynaut	Level up	15
Pyukumuku	Level up	17
Heracross	Level up	19
Breloom	Level up	22
Hitmontop	Level up	28
Slakoth	Level up	30
Vigoroth	Level up	33
Slaking	Level up	33
Sudowoodo	Level up	36
Bonsly	Level up	36
Mudbray	Level up	36
Mudsdale	Level up	42
Buzzwole	Level up	43
Meditite	Level up	44
Medicham	Level up	53
Charmander	Egg
Rattata	Egg
Sandshrew	Egg
Nidoran♀	Egg
Nidoran♂	Egg
Paras	Egg
Mankey	Egg
Machop	Egg
Rhyhorn	Egg
Chansey	Egg
Kangaskhan	Egg
Scyther	Egg
Snorlax	Egg
Chikorita	Egg
Aipom	Egg
Wooper	Egg
Pineco	Egg
Gligar	Egg
Sneasel	Egg
Teddiursa	Egg
Houndour	Egg
Phanpy	Egg
Tyrogue	Egg
Torchic	Egg
Mudkip	Egg
Lotad	Egg
Makuhita	Egg
Cacnea	Egg
Zangoose	Egg
Chimchar	Egg
Shieldon	Egg
Shellos	Egg
Happiny	Egg
Munchlax	Egg
Croagunk	Egg
Timburr	Egg
Sandile	Egg
Dwebble	Egg
Scraggy	Egg
Zorua	Egg
Karrablast	Egg
Axew	Egg
Goomy	Egg
Jangmo-o	Egg

Omega Ruby and Alpha Sapphire: 59 species

Species	Method	Level
Hitmonchan	Level up	1, 61
Wobbuffet	Level up	1
Riolu	Level up	6
Lucario	Level up	6
Wynaut	Level up	15
Heracross	Level up	19
Sawk	Level up	21
Breloom	Level up	22
Hitmontop	Level up	28
Slakoth	Level up	30
Sudowoodo	Level up	33
Vigoroth	Level up	33
Slaking	Level up	33
Bonsly	Level up	33
Meditite	Level up	44
Medicham	Level up	53
Charmander	Egg
Rattata	Egg
Sandshrew	Egg
Nidoran♀	Egg
Nidoran♂	Egg
Paras	Egg
Mankey	Egg
Machop	Egg
Rhyhorn	Egg
Chansey	Egg
Kangaskhan	Egg
Scyther	Egg
Snorlax	Egg
Chikorita	Egg
Aipom	Egg
Wooper	Egg
Pineco	Egg
Gligar	Egg
Sneasel	Egg
Teddiursa	Egg
Houndour	Egg
Phanpy	Egg
Tyrogue	Egg
Torchic	Egg
Mudkip	Egg
Lotad	Egg
Makuhita	Egg
Cacnea	Egg
Zangoose	Egg
Chimchar	Egg
Shieldon	Egg
Shellos	Egg
Happiny	Egg
Munchlax	Egg
Croagunk	Egg
Timburr	Egg
Sandile	Egg
Dwebble	Egg
Scraggy	Egg
Zorua	Egg
Karrablast	Egg
Axew	Egg
Goomy	Egg

X and Y: 57 species

Species	Method	Level
Hitmonchan	Level up	1, 61
Wobbuffet	Level up	1
Riolu	Level up	6
Lucario	Level up	6
Wynaut	Level up	15
Heracross	Level up	19
Sawk	Level up	21
Breloom	Level up	25
Hitmontop	Level up	28
Sudowoodo	Level up	33
Bonsly	Level up	33
Vigoroth	Level up	37
Slakoth	Level up	43
Slaking	Level up	43
Charmander	Egg
Rattata	Egg
Sandshrew	Egg
Nidoran♀	Egg
Nidoran♂	Egg
Paras	Egg
Mankey	Egg
Machop	Egg
Rhyhorn	Egg
Chansey	Egg
Kangaskhan	Egg
Scyther	Egg
Snorlax	Egg
Chikorita	Egg
Aipom	Egg
Wooper	Egg
Pineco	Egg
Gligar	Egg
Sneasel	Egg
Teddiursa	Egg
Houndour	Egg
Phanpy	Egg
Tyrogue	Egg
Torchic	Egg
Mudkip	Egg
Lotad	Egg
Makuhita	Egg
Cacnea	Egg
Zangoose	Egg
Chimchar	Egg
Shieldon	Egg
Shellos	Egg
Happiny	Egg
Munchlax	Egg
Croagunk	Egg
Timburr	Egg
Sandile	Egg
Dwebble	Egg
Scraggy	Egg
Zorua	Egg
Karrablast	Egg
Axew	Egg
Goomy	Egg