Grass
Grass and Flying types: weaknesses, resistances and Pokémon
Grass and Flying Pokémon take quadruple damage from Ice moves, take double damage from Fire, Poison, Flying and Rock moves, resist Grass, Water and Fighting moves and are immune to Ground moves.
The balance is even: 5 weaknesses and 4 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. Flying moves are super effective against Grass, Fighting and Bug and not very effective against Electric, Rock and Steel.
To beat these Pokémon, your best pick is Ice moves. Avoid Grass, Water, Fighting and Ground moves, which deal little or no damage.
There are 6 Pokémon with this combination, such as Hoppip, Skiploom, Jumpluff and Tropius.