Fairy does ×2 to Fighting

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

64 Fairy and 73 Fighting species among the 1025 this site covers.

Attacker, Psychic and Fairy Hatterene sprite

damage×2Generations VI to IX

Defender, Bug and Fighting Buzzwole sprite

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

Strongest Fairy attackers

Hatterene leads Fairy at Sp. Atk 136

Sturdiest Fighting defenders

Dual types that change the answer