Generally, it depends on the Pokemon you are facing. If you are facing a Swampert, it's best to use Grass because it's secondary type is ground. For most Wild Pokemon, the ones you find Fishing or Surfing are weakest again Electric than Grass but there are more Pokemon that are weak against Grass.
electric types and grass types.
Dragon types(Garchomp, Haxorus etc) Ice types (Froslass, Weavile etc)
electric and grass are all I can think of
Grass and Electric types
Electric and grass
Electric and Grass type attacks are effective against Water types. Water type attacks are bad against Grass, Dragon and other Water types. Note that almost all Water Types can learn an Ice type move, so be careful when sending in Grass types to counter them.
Water-Type moves are weak against Grass-Types, Dragon-Types, and other Water-Types. Water-Type Pokémon are weak against Electric-Types and Grass-Types.
I would use grass, ground or dragon types. Some aren't effective against electric type, but electric isn't very effective against them.
Grass and Electric can defeat Water types easily.
grass pokemon examples: chikorita, bulbasour, oddish, tropius, turtwig, and bellsprout but theres more!
fire ground rock
Water-type Pokemon are weak against Electric and Grass-type attacks.