Flash Cannon is learned by 26 species by level and 135 by machine

Effect, in PokéAPI's words

“Has a chance to lower the target’s Special Defense by one stage.”

Who learns it

135 species in all, 8 of 14 games shown

Scarlet and Violet: 95 species

Species	Method	Level
Blastoise	Level up, Machine	Evolve
Metagross	Level up, Machine	16
Metang	Level up, Machine	18
Registeel	Level up, Machine	24
Solgaleo	Level up, Machine	28
Tinkatink	Level up, Machine	31
Tinkatuff	Level up, Machine	31
Tinkaton	Level up, Machine	31
Magnemite	Level up, Machine	32
Dialga	Level up, Machine	32
Magneton	Level up, Machine	34
Magnezone	Level up, Machine	34
Klefki	Level up, Machine	36
Iron Crown	Level up, Machine	42
Duraludon	Level up, Machine	54
Archaludon	Level up, Machine	54
Magearna	Level up, Machine	72
Horsea	Machine
Seadra	Machine
Mew	Machine
Forretress	Machine
Scizor	Machine
Skarmory	Machine
Kingdra	Machine
Nosepass	Machine
Numel	Machine
Camerupt	Machine
Spoink	Machine
Grumpig	Machine
Regirock	Machine
Regice	Machine
Jirachi	Machine
Deoxys	Machine
Empoleon	Machine
Shieldon	Machine
Bastiodon	Machine
Bronzor	Machine
Bronzong	Machine
Lucario	Machine
Rhyperior	Machine
Probopass	Machine
Heatran	Machine
Arceus	Machine
Solosis	Machine
Duosion	Machine
Reuniclus	Machine
Eelektrik	Machine
Eelektross	Machine
Cryogonal	Machine
Golurk	Machine
Pawniard	Machine
Bisharp	Machine
Hydreigon	Machine
Cobalion	Machine
Thundurus	Machine
Zekrom	Machine
Kyurem	Machine
Clauncher	Machine
Clawitzer	Machine
Carbink	Machine
Avalugg	Machine
Diancie	Machine
Volcanion	Machine
Toucannon	Machine
Vikavolt	Machine
Sandygast	Machine
Palossand	Machine
Kommo-o	Machine
Necrozma	Machine
Corviknight	Machine
Cufant	Machine
Copperajah	Machine
Zacian	Machine
Zamazenta	Machine
Eternatus	Machine
Nacli	Machine
Naclstack	Machine
Garganacl	Machine
Armarouge	Machine
Toedscool	Machine
Toedscruel	Machine
Espathra	Machine
Varoom	Machine
Revavroom	Machine
Orthworm	Machine
Glimmora	Machine
Kingambit	Machine
Great Tusk	Machine
Sandy Shocks	Machine
Iron Treads	Machine
Iron Jugulis	Machine
Iron Moth	Machine
Gholdengo	Machine
Miraidon	Machine
Terapagos	Machine

Legends Arceus: 8 species

Species	Method	Level
Empoleon	Level up	Evolve
Magnemite	Level up	25
Magneton	Level up	25
Magnezone	Level up	25
Bronzor	Level up	34
Bronzong	Level up	34
Probopass	Level up	38
Dialga	Level up	55

Brilliant Diamond and Shining Pearl: 36 species

Species	Method	Level
Blastoise	Level up, Machine	Evolve, 1
Metagross	Level up, Machine	16
Metang	Level up, Machine	18
Registeel	Level up, Machine	24
Magnemite	Level up, Machine	32
Dialga	Level up, Machine	32
Magneton	Level up, Machine	34
Magnezone	Level up, Machine	34
Onix	Machine
Horsea	Machine
Seadra	Machine
Staryu	Machine
Starmie	Machine
Mew	Machine
Forretress	Machine
Steelix	Machine
Scizor	Machine
Octillery	Machine
Skarmory	Machine
Kingdra	Machine
Mawile	Machine
Aggron	Machine
Camerupt	Machine
Armaldo	Machine
Regirock	Machine
Regice	Machine
Jirachi	Machine
Empoleon	Machine
Shieldon	Machine
Bastiodon	Machine
Bronzor	Machine
Bronzong	Machine
Lucario	Machine
Rhyperior	Machine
Probopass	Machine
Heatran	Machine

Sword and Shield: 87 species

Species	Method	Level
Blastoise	Level up, Machine	Evolve, 1
Metagross	Level up, Machine	16
Metang	Level up, Machine	18
Ferroseed	Level up, Machine	20
Ferrothorn	Level up, Machine	20
Registeel	Level up, Machine	24
Solgaleo	Level up, Machine	28
Magnemite	Level up, Machine	32
Dialga	Level up, Machine	32
Magneton	Level up, Machine	34
Magnezone	Level up, Machine	34
Klefki	Level up, Machine	36
Celesteela	Level up, Machine	40
Meltan	Level up, Machine	40
Melmetal	Level up, Machine	40
Duraludon	Level up, Machine	54
Magearna	Level up, Machine	72
Onix	Machine
Horsea	Machine
Seadra	Machine
Staryu	Machine
Starmie	Machine
Mew	Machine
Steelix	Machine
Scizor	Machine
Octillery	Machine
Skarmory	Machine
Kingdra	Machine
Mawile	Machine
Aggron	Machine
Armaldo	Machine
Regirock	Machine
Regice	Machine
Jirachi	Machine
Bronzor	Machine
Bronzong	Machine
Lucario	Machine
Rhyperior	Machine
Heatran	Machine
Roggenrola	Machine
Boldore	Machine
Gigalith	Machine
Sigilyph	Machine
Solosis	Machine
Duosion	Machine
Reuniclus	Machine
Vanillite	Machine
Vanillish	Machine
Vanilluxe	Machine
Klink	Machine
Klang	Machine
Klinklang	Machine
Beheeyem	Machine
Cryogonal	Machine
Druddigon	Machine
Golurk	Machine
Durant	Machine
Hydreigon	Machine
Cobalion	Machine
Thundurus	Machine
Zekrom	Machine
Kyurem	Machine
Genesect	Machine
Honedge	Machine
Doublade	Machine
Aegislash	Machine
Spritzee	Machine
Aromatisse	Machine
Clauncher	Machine
Clawitzer	Machine
Amaura	Machine
Aurorus	Machine
Bergmite	Machine
Avalugg	Machine
Xerneas	Machine
Volcanion	Machine
Vikavolt	Machine
Silvally	Machine
Turtonator	Machine
Dhelmise	Machine
Kommo-o	Machine
Necrozma	Machine
Stakataka	Machine
Corviknight	Machine
Copperajah	Machine
Zamazenta	Machine
Eternatus	Machine

Let's Go Pikachu and Let's Go Eevee: 11 species

Species	Method	Level
Blastoise	Level up, Machine	1
Magnemite	Level up, Machine	38
Meltan	Level up, Machine	45
Melmetal	Level up, Machine	45
Magneton	Level up, Machine	46
Onix	Machine
Horsea	Machine
Seadra	Machine
Staryu	Machine
Starmie	Machine
Mew	Machine

Ultra Sun and Ultra Moon: 89 species

Species	Method	Level
Blastoise	Level up, Machine	1
Solgaleo	Level up, Machine	23
Magnemite	Level up, Machine	31
Magneton	Level up, Machine	33
Magnezone	Level up, Machine	33
Celesteela	Level up, Machine	37
Magearna	Level up, Machine	41
Registeel	Level up, Machine	43
Dialga	Level up, Machine	50
Ferroseed	Level up, Machine	52
Ferrothorn	Level up, Machine	61
Onix	Machine
Horsea	Machine
Seadra	Machine
Staryu	Machine
Starmie	Machine
Mew	Machine
Forretress	Machine
Steelix	Machine
Scizor	Machine
Octillery	Machine
Skarmory	Machine
Kingdra	Machine
Mawile	Machine
Aggron	Machine
Camerupt	Machine
Armaldo	Machine
Metang	Machine
Metagross	Machine
Regice	Machine
Jirachi	Machine
Deoxys	Machine
Empoleon	Machine
Shieldon	Machine
Bastiodon	Machine
Bronzor	Machine
Bronzong	Machine
Lucario	Machine
Rhyperior	Machine
Probopass	Machine
Heatran	Machine
Arceus	Machine
Roggenrola	Machine
Boldore	Machine
Gigalith	Machine
Sigilyph	Machine
Solosis	Machine
Duosion	Machine
Reuniclus	Machine
Vanillite	Machine
Vanillish	Machine
Vanilluxe	Machine
Klink	Machine
Klang	Machine
Klinklang	Machine
Eelektrik	Machine
Eelektross	Machine
Cryogonal	Machine
Druddigon	Machine
Golurk	Machine
Durant	Machine
Hydreigon	Machine
Cobalion	Machine
Thundurus	Machine
Zekrom	Machine
Kyurem	Machine
Genesect	Machine
Honedge	Machine
Doublade	Machine
Aegislash	Machine
Spritzee	Machine
Aromatisse	Machine
Clauncher	Machine
Clawitzer	Machine
Amaura	Machine
Aurorus	Machine
Klefki	Machine
Bergmite	Machine
Avalugg	Machine
Xerneas	Machine
Volcanion	Machine
Toucannon	Machine
Vikavolt	Machine
Silvally	Machine
Turtonator	Machine
Dhelmise	Machine
Kommo-o	Machine
Necrozma	Machine
Stakataka	Machine

Sun and Moon: 88 species

Species	Method	Level
Blastoise	Level up, Machine	1
Solgaleo	Level up, Machine	23
Magnemite	Level up, Machine	31
Magneton	Level up, Machine	33
Magnezone	Level up, Machine	33
Celesteela	Level up, Machine	37
Magearna	Level up, Machine	41
Registeel	Level up, Machine	43
Dialga	Level up, Machine	50
Ferroseed	Level up, Machine	52
Ferrothorn	Level up, Machine	61
Onix	Machine
Horsea	Machine
Seadra	Machine
Staryu	Machine
Starmie	Machine
Mew	Machine
Forretress	Machine
Steelix	Machine
Scizor	Machine
Octillery	Machine
Skarmory	Machine
Kingdra	Machine
Mawile	Machine
Aggron	Machine
Camerupt	Machine
Armaldo	Machine
Metang	Machine
Metagross	Machine
Regice	Machine
Jirachi	Machine
Deoxys	Machine
Empoleon	Machine
Shieldon	Machine
Bastiodon	Machine
Bronzor	Machine
Bronzong	Machine
Lucario	Machine
Rhyperior	Machine
Probopass	Machine
Heatran	Machine
Arceus	Machine
Roggenrola	Machine
Boldore	Machine
Gigalith	Machine
Sigilyph	Machine
Solosis	Machine
Duosion	Machine
Reuniclus	Machine
Vanillite	Machine
Vanillish	Machine
Vanilluxe	Machine
Klink	Machine
Klang	Machine
Klinklang	Machine
Eelektrik	Machine
Eelektross	Machine
Cryogonal	Machine
Druddigon	Machine
Golurk	Machine
Durant	Machine
Hydreigon	Machine
Cobalion	Machine
Thundurus	Machine
Zekrom	Machine
Kyurem	Machine
Genesect	Machine
Honedge	Machine
Doublade	Machine
Aegislash	Machine
Spritzee	Machine
Aromatisse	Machine
Clauncher	Machine
Clawitzer	Machine
Amaura	Machine
Aurorus	Machine
Klefki	Machine
Bergmite	Machine
Avalugg	Machine
Xerneas	Machine
Volcanion	Machine
Toucannon	Machine
Vikavolt	Machine
Silvally	Machine
Turtonator	Machine
Dhelmise	Machine
Kommo-o	Machine
Necrozma	Machine

Omega Ruby and Alpha Sapphire: 78 species

Species	Method	Level
Blastoise	Level up, Machine	1
Magnemite	Level up, Machine	31
Magneton	Level up, Machine	33
Magnezone	Level up, Machine	33
Registeel	Level up, Machine	43
Dialga	Level up, Machine	50
Ferroseed	Level up, Machine	52
Ferrothorn	Level up, Machine	61
Onix	Machine
Horsea	Machine
Seadra	Machine
Staryu	Machine
Starmie	Machine
Mew	Machine
Forretress	Machine
Steelix	Machine
Scizor	Machine
Octillery	Machine
Skarmory	Machine
Kingdra	Machine
Mawile	Machine
Aggron	Machine
Camerupt	Machine
Armaldo	Machine
Metang	Machine
Metagross	Machine
Regice	Machine
Jirachi	Machine
Deoxys	Machine
Empoleon	Machine
Shieldon	Machine
Bastiodon	Machine
Bronzor	Machine
Bronzong	Machine
Lucario	Machine
Rhyperior	Machine
Probopass	Machine
Heatran	Machine
Arceus	Machine
Roggenrola	Machine
Boldore	Machine
Gigalith	Machine
Sigilyph	Machine
Solosis	Machine
Duosion	Machine
Reuniclus	Machine
Vanillite	Machine
Vanillish	Machine
Vanilluxe	Machine
Klink	Machine
Klang	Machine
Klinklang	Machine
Eelektrik	Machine
Eelektross	Machine
Cryogonal	Machine
Druddigon	Machine
Golurk	Machine
Durant	Machine
Hydreigon	Machine
Cobalion	Machine
Thundurus	Machine
Zekrom	Machine
Kyurem	Machine
Genesect	Machine
Honedge	Machine
Doublade	Machine
Aegislash	Machine
Spritzee	Machine
Aromatisse	Machine
Clauncher	Machine
Clawitzer	Machine
Amaura	Machine
Aurorus	Machine
Klefki	Machine
Bergmite	Machine
Avalugg	Machine
Xerneas	Machine
Volcanion	Machine