Misty Explosion is learned by 18 species by machine and 21 by tutor

Effect, in PokéAPI's words

“If Misty Terrain is active and the user is grounded, this move has its power increased by 50%.”

Who learns it

24 species in all, 2 games

Scarlet and Violet: 18 species

Species	Method	Level
Clefairy	Machine
Clefable	Machine
Jigglypuff	Machine
Wigglytuff	Machine
Mew	Machine
Marill	Machine
Azumarill	Machine
Gardevoir	Machine
Florges	Machine
Sylveon	Machine
Carbink	Machine
Diancie	Machine
Primarina	Machine
Magearna	Machine
Hatterene	Machine
Alcremie	Machine
Enamorus	Machine
Scream Tail	Machine

Sword and Shield: 21 species

Species	Method	Level
Clefairy	Tutor
Clefable	Tutor
Jigglypuff	Tutor
Wigglytuff	Tutor
Mew	Tutor
Marill	Tutor
Azumarill	Tutor
Gardevoir	Tutor
Musharna	Tutor
Spritzee	Tutor
Aromatisse	Tutor
Swirlix	Tutor
Slurpuff	Tutor
Sylveon	Tutor
Carbink	Tutor
Xerneas	Tutor
Diancie	Tutor
Primarina	Tutor
Magearna	Tutor
Hatterene	Tutor
Alcremie	Tutor