GhostFairy
Ghost and Fairy types: weaknesses, resistances and Pokémon
Ghost and Fairy Pokémon take double damage from Ghost and Steel moves, resist Bug moves and are immune to Normal, Fighting and Dragon moves.
The balance is even: 2 weaknesses and 4 resistances or immunities.
Ghost moves are super effective against Psychic and Ghost and not very effective against Dark. Fairy moves are super effective against Fighting, Dragon and Dark and not very effective against Fire, Poison and Steel.
To beat these Pokémon, your best pick is Ghost and Steel moves. Avoid Bug, Normal, Fighting and Dragon moves, which deal little or no damage.
There are 2 Pokémon with this combination, such as Mimikyu and Flutter Mane.