Poison does ×2 to Fairy

Generations VI to IX, single types. The other way round, Fairy against Poison, is ×½.

83 Poison and 64 Fairy species among the 1025 this site covers.

Attacker, Poison and Dragon Eternatus sprite

damage×2Generations VI to IX

Defender, Fairy Florges sprite

Florges #0671

Fairy did not exist in Generation I and Generations II to V, so Poison against Fairy has no value there.

Strongest Poison attackers

Eternatus leads Poison at Sp. Atk 145

Sturdiest Fairy defenders

Dual types that change the answer