Dark does ×1 to Ground

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

69 Dark and 75 Ground species among the 1025 this site covers.

Attacker, Dragon and Dark Roaring Moon sprite

damage×1Generations VI to IX

Defender, Steel and Ground Steelix sprite

Steelix #0208

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

Strongest Dark attackers

Roaring Moon leads Dark at Atk 139

Sturdiest Ground defenders

Dual types that change the answer