Here's why:
* Ghost: Ghost-type moves are super effective against Ghost-type Pokémon. This means they do double the damage.
* Dark: Dark-type moves are also super effective against Ghost-type Pokémon.
It's important to note that Ghost-type Pokémon are immune to Normal and Fighting type moves. This means these moves will have no effect on them.
Here are some examples of Pokémon that can effectively counter Ghost-type Pokémon:
* Gengar: A Ghost/Poison type, Gengar can learn powerful Ghost and Dark-type moves like Shadow Ball and Lick.
* Houndoom: A Dark/Fire type, Houndoom can learn strong Dark-type moves like Foul Play and Crunch.
* Tyranitar: A Rock/Dark type, Tyranitar can learn powerful Dark-type moves like Crunch and Dark Pulse.
* Spiritomb: A Ghost/Dark type, Spiritomb can learn powerful Ghost-type moves like Shadow Sneak and Shadow Ball.
Remember to consider the individual Pokémon's moveset and stats when deciding which Pokémon to use against a Ghost-type opponent.