Steel does ×1 to Dark

Generations VI to IX, single types. The other way round, Dark against Steel, is ×1.

65 Steel and 69 Dark species among the 1025 this site covers.

Attacker, Grass and Steel Kartana sprite

Kartana #0798

damage×1Generations VI to IX

Defender, Dark and Grass Wo-Chien sprite

Steel and Dark did not exist in Generation I, so Steel against Dark has no value there.

Strongest Steel attackers

Kartana leads Steel at Atk 181

Sturdiest Dark defenders

Dual types that change the answer