Psychic and Ground type.
Poison is strong against grass type Pokémon.
Psychic and Ground
ground and physic Pokemon are super effective against poison Pokemon
1.Fighting Types 2.Poison
Ground type Pokémon beat fire, steel, rock, electric and poison type Pokémon.
A Poison/Ground-type Pokemon is weak to Psychic, Ground, Water, and Ice-type attacks. Nidoking and Nidoqueen are the only two Pokemon with this typing.
Almost any type can defeat a Fairy-type Pokemon, but its weaknesses are Poison and Steel. They are immune to Dragon and halves the damage to Bug, Fighting, and Dark-type moves.
If you have an Ice type Pokemon that can work too. So can Poison, Bug, and Flying types.
Any fire type pokemon, or a pokemon with a fire type move, I think poison too...
That would depend on the game since in Ruby and Sapphire, Wallace is a Gym Leader and he has Pokemon such as Luvdisc which is a Water-type, Seaking which is a Water-type, Milotic which is a Water-type, Sealeo which is an Ice and Water-type and Whiscash which is a Water and Ground-type and in Emerald he is the Champion and he has Wailord and Milotic which are Water-types, Tentacruel which is a Water and Poison-type, Gyarados which is a Water and Flying-type and Ludicolo which is a Water and Grass-type. Electric-types such as Pikachu, Jolteon, Ampharos, Zapdos and Raikou can beat most of his Water-types as well as Gyarados, Psychic-types can also beat Tentacruel due to it being part Poison-type, Grass-types can beat Whiscash and either Flying, Poison or Bug-types can beat Ludicolo.
Fire.The fire will burn the grass and also ice,flying,poison,and bug type :D
Ground types and psychic types beat poison types.