DragonDark
Dragon and Dark types: weaknesses, resistances and Pokémon
Dragon and Dark Pokémon take quadruple damage from Fairy moves, take double damage from Ice, Fighting, Bug and Dragon moves, resist Fire, Water, Grass, Electric, Ghost and Dark moves and are immune to Psychic moves.
The balance is even: 5 weaknesses and 7 resistances or immunities.
Dragon moves are super effective against Dragon and not very effective against Steel. Dark moves are super effective against Psychic and Ghost and not very effective against Fighting, Dark and Fairy.
To beat these Pokémon, your best pick is Fairy moves. Avoid Fire, Water, Grass and Electric moves, which deal little or no damage.
There are 5 Pokémon with this combination, such as Deino, Zweilous, Hydreigon and Guzzlord.