Coil is learned by 19 species by level and 1 by egg

Effect, in PokéAPI's words

“Raises the user’s Attack, Defense, and accuracy by one stage each.”

Who learns it

20 species in all, 8 of 9 games shown

Scarlet and Violet: 15 species

Species	Method	Level
Furret	Level up	1
Eelektross	Level up	1
Snivy	Level up	31
Servine	Level up	36
Serperior	Level up	38
Ekans	Level up	44
Dunsparce	Level up	44
Seviper	Level up	44
Dudunsparce	Level up	44
Silicobra	Level up	45
Milotic	Level up	48
Sandaconda	Level up	49
Eelektrik	Level up	54
Arbok	Level up	56
Orthworm	Egg

Brilliant Diamond and Shining Pearl: 8 species

Species	Method	Level
Furret	Level up	1
Ekans	Level up	44
Seviper	Level up	44
Huntail	Level up	45
Gorebyss	Level up	45
Dunsparce	Level up	48
Milotic	Level up	48
Arbok	Level up	56

Sword and Shield: 7 species

Species	Method	Level
Sizzlipede	Level up	25
Centiskorch	Level up	25
Silicobra	Level up	45
Dunsparce	Level up	48
Milotic	Level up	48
Sandaconda	Level up	49
Zygarde	Level up	72

Ultra Sun and Ultra Moon: 14 species

Species	Method	Level
Furret	Level up	1
Eelektross	Level up	1
Dunsparce	Level up	31
Snivy	Level up	31
Servine	Level up	36
Serperior	Level up	38
Milotic	Level up	41
Ekans	Level up	44
Seviper	Level up	44
Huntail	Level up	45
Gorebyss	Level up	45
Eelektrik	Level up	54
Arbok	Level up	56
Zygarde	Level up	72

Sun and Moon: 14 species

Species	Method	Level
Furret	Level up	1
Eelektross	Level up	1
Dunsparce	Level up	28
Snivy	Level up	31
Servine	Level up	36
Serperior	Level up	38
Milotic	Level up	41
Ekans	Level up	44
Seviper	Level up	44
Huntail	Level up	45
Gorebyss	Level up	45
Eelektrik	Level up	54
Arbok	Level up	56
Zygarde	Level up	72

Omega Ruby and Alpha Sapphire: 13 species

Species	Method	Level
Eelektross	Level up	1
Snivy	Level up	31
Servine	Level up	36
Dunsparce	Level up	37
Serperior	Level up	38
Ekans	Level up	44
Milotic	Level up	44
Huntail	Level up	45
Gorebyss	Level up	45
Seviper	Level up	46
Eelektrik	Level up	54
Arbok	Level up	56
Zygarde	Level up	80

X and Y: 10 species

Species	Method	Level
Eelektross	Level up	1
Snivy	Level up	31
Servine	Level up	36
Dunsparce	Level up	37
Serperior	Level up	38
Ekans	Level up	44
Seviper	Level up	48
Eelektrik	Level up	54
Arbok	Level up	56
Zygarde	Level up	80

Black 2 and White 2: 8 species

Species	Method	Level
Snivy	Level up	31
Servine	Level up	36
Dunsparce	Level up	37
Serperior	Level up	38
Ekans	Level up	44
Seviper	Level up	49
Eelektrik	Level up	54
Arbok	Level up	56