Heavy Slam is learned by 33 species by level, 122 by machine and 7 by egg

Effect, in PokéAPI's words

“Power is higher when the user weighs more than the target, up to a maximum of 120.”

Who learns it

122 species in all, 8 of 9 games shown

Scarlet and Violet: 99 species

Species	Method	Level
Forretress	Level up, Machine	Evolve
Copperajah	Level up, Machine	Evolve
Golem	Level up, Machine	1
Snorlax	Level up, Machine	32
Bronzor	Level up, Machine	32
Bronzong	Level up, Machine	32
Mudbray	Level up, Machine	32
Mudsdale	Level up, Machine	34
Nacli	Level up, Machine	35
Golett	Level up, Machine	40
Golurk	Level up, Machine	40
Naclstack	Level up, Machine	41
Sandy Shocks	Level up, Machine	42
Garganacl	Level up, Machine	44
Makuhita	Level up, Machine	46
Shieldon	Level up, Machine	46
Registeel	Level up, Machine	48
Terapagos	Level up, Machine	50
Hariyama	Level up, Machine	54
Stonjourner	Level up, Machine	54
Dondozo	Level up, Machine	55
Iron Treads	Level up, Machine	56
Bastiodon	Level up, Machine	58
Regigigas	Level up, Machine	60
Iron Hands	Level up, Machine	77
Graveler	Machine
Magnemite	Machine
Magneton	Machine
Rhyhorn	Machine
Rhydon	Machine
Mew	Machine
Phanpy	Machine, Egg
Donphan	Machine
Tyranitar	Machine
Slaking	Machine
Nosepass	Machine
Numel	Machine, Egg
Camerupt	Machine
Torkoal	Machine
Metang	Machine
Metagross	Machine
Regirock	Machine
Regice	Machine
Kyogre	Machine
Groudon	Machine
Turtwig	Machine
Grotle	Machine
Torterra	Machine
Rampardos	Machine
Hippowdon	Machine
Magnezone	Machine
Rhyperior	Machine
Mamoswine	Machine
Probopass	Machine
Dialga	Machine
Palkia	Machine
Heatran	Machine
Arceus	Machine
Tepig	Machine
Pignite	Machine
Emboar	Machine
Eelektross	Machine
Cubchoo	Machine
Beartic	Machine
Cobalion	Machine
Carbink	Machine
Avalugg	Machine
Volcanion	Machine
Solgaleo	Machine
Magearna	Machine
Corviknight	Machine
Carkol	Machine
Coalossal	Machine
Flapple	Machine
Appletun	Machine
Perrserker	Machine
Cufant	Machine
Duraludon	Machine
Zamazenta	Machine
Glastrier	Machine
Ursaluna	Machine
Tinkaton	Machine
Revavroom	Machine
Orthworm	Machine
Cetoddle	Machine
Cetitan	Machine
Clodsire	Machine
Dudunsparce	Machine
Great Tusk	Machine
Slither Wing	Machine
Iron Thorns	Machine
Gholdengo	Machine
Ting-Lu	Machine
Koraidon	Machine
Miraidon	Machine
Archaludon	Machine
Hydrapple	Machine
Raging Bolt	Machine
Iron Crown	Machine

Brilliant Diamond and Shining Pearl: 21 species

Species	Method	Level
Golem	Level up	1, 60
Forretress	Level up	1, 64
Wailmer	Level up	21
Wailord	Level up	21
Snorlax	Level up	32
Bronzor	Level up	32
Bronzong	Level up	32
Makuhita	Level up	46
Shieldon	Level up	46
Registeel	Level up	48
Aron	Level up	52
Hariyama	Level up	54
Bastiodon	Level up	58
Regigigas	Level up	60
Lairon	Level up	64
Aggron	Level up	72
Machop	Egg
Onix	Egg
Phanpy	Egg
Numel	Egg
Turtwig	Egg

Sword and Shield: 60 species

Species	Method	Level
Copperajah	Level up, Machine	Evolve, 1
Wailmer	Level up, Machine	21
Wailord	Level up, Machine	21
Snorlax	Level up, Machine	32
Bronzor	Level up, Machine	32
Bronzong	Level up, Machine	32
Mudbray	Level up, Machine	32
Mudsdale	Level up, Machine	34
Dhelmise	Level up, Machine	36
Golett	Level up, Machine	40
Golurk	Level up, Machine	40
Registeel	Level up, Machine	48
Guzzlord	Level up, Machine	50
Aron	Level up, Machine	52
Stonjourner	Level up, Machine	54
Regigigas	Level up, Machine	60
Celesteela	Level up, Machine	60
Lairon	Level up, Machine	64
Aggron	Level up, Machine	72
Machop	Machine
Machoke	Machine
Machamp	Machine
Onix	Machine
Rhydon	Machine
Mew	Machine
Steelix	Machine
Miltank	Machine
Tyranitar	Machine
Walrein	Machine
Regirock	Machine
Regice	Machine
Kyogre	Machine
Groudon	Machine
Hippowdon	Machine
Magnezone	Machine
Rhyperior	Machine
Mamoswine	Machine
Dialga	Machine
Palkia	Machine
Heatran	Machine
Roggenrola	Machine
Boldore	Machine
Gigalith	Machine
Crustle	Machine
Ferrothorn	Machine
Beartic	Machine
Avalugg	Machine
Volcanion	Machine
Turtonator	Machine
Solgaleo	Machine
Stakataka	Machine
Melmetal	Machine
Corviknight	Machine
Carkol	Machine
Coalossal	Machine
Flapple	Machine
Appletun	Machine
Perrserker	Machine
Duraludon	Machine
Glastrier	Machine

Ultra Sun and Ultra Moon: 28 species

Species	Method	Level
Golurk	Level up	Evolve, 1
Golem	Level up	1, 60
Forretress	Level up	1, 64
Wailord	Level up	1, 65
Regigigas	Level up	1, 90
Mudbray	Level up	31
Mudsdale	Level up	34
Makuhita	Level up	46
Aron	Level up	46
Shieldon	Level up	46
Bronzor	Level up	49
Snorlax	Level up	50
Dhelmise	Level up	50
Lairon	Level up	51
Wailmer	Level up	53
Hariyama	Level up	54
Aggron	Level up	57
Bastiodon	Level up	58
Bronzong	Level up	58
Guzzlord	Level up	59
Celesteela	Level up	67
Machop	Egg
Onix	Egg
Phanpy	Egg
Numel	Egg
Turtwig	Egg
Tepig	Egg
Roggenrola	Egg

Sun and Moon: 26 species

Species	Method	Level
Golurk	Level up	Evolve, 1
Golem	Level up	1, 60
Forretress	Level up	1, 64
Wailord	Level up	1, 65
Regigigas	Level up	1, 90
Mudbray	Level up	31
Mudsdale	Level up	34
Makuhita	Level up	46
Aron	Level up	46
Shieldon	Level up	46
Bronzor	Level up	49
Snorlax	Level up	50
Dhelmise	Level up	50
Lairon	Level up	51
Wailmer	Level up	53
Hariyama	Level up	54
Aggron	Level up	57
Bastiodon	Level up	58
Bronzong	Level up	58
Guzzlord	Level up	59
Celesteela	Level up	67
Machop	Egg
Onix	Egg
Phanpy	Egg
Tepig	Egg
Roggenrola	Egg

Omega Ruby and Alpha Sapphire: 21 species

Species	Method	Level
Golem	Level up	1, 60
Forretress	Level up	1, 70
Wailord	Level up	1, 65
Regigigas	Level up	1, 90
Golurk	Level up	43
Makuhita	Level up	46
Aron	Level up	46
Shieldon	Level up	46
Bronzor	Level up	49
Snorlax	Level up	50
Lairon	Level up	51
Wailmer	Level up	53
Hariyama	Level up	54
Aggron	Level up	57
Bastiodon	Level up	58
Bronzong	Level up	58
Machop	Egg
Onix	Egg
Phanpy	Egg
Tepig	Egg
Roggenrola	Egg

X and Y: 21 species

Species	Method	Level
Golem	Level up	1, 69
Forretress	Level up	1, 70
Regigigas	Level up	1, 90
Aron	Level up	43
Golurk	Level up	43
Makuhita	Level up	46
Shieldon	Level up	46
Bronzor	Level up	49
Snorlax	Level up	50
Wailmer	Level up	50
Lairon	Level up	51
Aggron	Level up	57
Bastiodon	Level up	58
Bronzong	Level up	58
Hariyama	Level up	62
Wailord	Level up	70
Machop	Egg
Onix	Egg
Phanpy	Egg
Tepig	Egg
Roggenrola	Egg

Black 2 and White 2: 21 species

Species	Method	Level
Aron	Level up	43
Golurk	Level up	43
Makuhita	Level up	46
Shieldon	Level up	46
Bronzor	Level up	49
Wailmer	Level up	50
Lairon	Level up	51
Snorlax	Level up	52
Aggron	Level up	57
Bastiodon	Level up	58
Bronzong	Level up	58
Hariyama	Level up	62
Golem	Level up	69
Forretress	Level up	70
Wailord	Level up	70
Regigigas	Level up	90
Machop	Egg
Onix	Egg
Phanpy	Egg
Tepig	Egg
Roggenrola	Egg