Grass and Dark types: weaknesses, resistances and Pokémon
Grass and Dark Pokémon take quadruple damage from Bug moves, take double damage from Fire, Ice, Fighting, Poison, Flying and Fairy moves, resist Water, Grass, Electric, Ground, Ghost and Dark moves and are immune to Psychic moves.
The balance is even: 7 weaknesses and 7 resistances or immunities.
Grass moves are super effective against Water, Ground and Rock and not very effective against Fire, Grass, Poison, Flying, Bug, Dragon and Steel. Dark moves are super effective against Psychic and Ghost and not very effective against Fighting, Dark and Fairy.
To beat these Pokémon, your best pick is Bug moves. Avoid Water, Grass, Electric and Ground moves, which deal little or no damage.
There are 7 Pokémon with this combination, such as Nuzleaf, Shiftry, Cacturne and Zarude.