Route 4: 16 species in 1 game

16 species, 2 versions

SwordShield

Sword: 16 species
Species	Method	Levels	Chance	Game page
Pikachu	Walking in the overworld	14 to 16	5%	All places
Diglett	Special overworld spawn in a fixed location	17	100%	All places
Goldeen	Fishing at bubbling spots in the water	13 to 15	10%	All places
Magikarp	Fishing at bubbling spots in the water	13 to 15	70%	All places
Eevee	Walking in the overworld	14 to 16	1%	All places
Electrike	Walking in the overworld	14 to 16	30%	All places
Budew	Walking in tall grass or a cave	13 to 15	4%	All places
Joltik	Walking in tall grass or a cave	13 to 15	10%	All places
Ferroseed	Walking in tall grass or a cave	13 to 15	1%	All places
Pumpkaboo	Walking in the overworld	14 to 16	10%	All places
Cutiefly	Walking in tall grass or a cave	13 to 15	5%	All places
Skwovet	Interacting with a berry tree	13 to 15	100%	All places
Wooloo	Walking in tall grass or a cave	13 to 15	25%	All places
Chewtle	Fishing at bubbling spots in the water	13 to 15	20%	All places
Yamper	Walking in the overworld	14 to 16	20%	All places
Milcery	Walking in tall grass or a cave	13 to 15	20%	All places

Shield: 16 species
Species	Method	Levels	Chance	Game page
Pikachu	Walking in the overworld	14 to 16	1%	All places
Diglett	Special overworld spawn in a fixed location	17	100%	All places
Goldeen	Fishing at bubbling spots in the water	13 to 15	10%	All places
Magikarp	Fishing at bubbling spots in the water	13 to 15	70%	All places
Eevee	Walking in the overworld	14 to 16	5%	All places
Electrike	Walking in the overworld	14 to 16	30%	All places
Budew	Walking in tall grass or a cave	13 to 15	4%	All places
Joltik	Walking in tall grass or a cave	13 to 15	10%	All places
Ferroseed	Walking in tall grass or a cave	13 to 15	1%	All places
Pumpkaboo	Walking in the overworld	14 to 16	10%	All places
Cutiefly	Walking in tall grass or a cave	13 to 15	5%	All places
Skwovet	Interacting with a berry tree	13 to 15	100%	All places
Wooloo	Walking in tall grass or a cave	13 to 15	25%	All places
Chewtle	Fishing at bubbling spots in the water	13 to 15	20%	All places
Yamper	Walking in the overworld	14 to 16	20%	All places
Milcery	Walking in tall grass or a cave	13 to 15	20%	All places