probably ghost type, rock type, or dark type. i also think water types effective
Yes. Ghost moves are super effective against Ghost type pokemon.
Ghost-Types are weak against Dark-Types and other Ghost-Types.
Sadly, normal is not super effective against any type. Beware, though. Fighting types are super effective against Normal!. Do not use Normal types against Ghost, or Ghost types against Normal, because they don't effect on each other!. (Example) Go Gengar! Go Snorlax! Gengar use Shadow Claw! It had no effect! Snorlax use Body Slam! It had no effect!
Normal types are strong against ghost types but at the same time they can't effect ghost types. Normal types have no strengths against any other type.
poison
fire is regularly effective against ghost types
Ghost types are weak against Dark and Ghost type moves.
dark and ghost types are both super effective against ghost types
Yes. Ghost moves are super effective against Ghost type pokemon.
Ghost and Dark-type Pokemon are super effective against Ghost types.
Bug, ghost, and dark types are most effective against psychic types.
Rock attacks can be used against ghost types. It will be regularly effective if the ghost type is ONLY ghost.
Psychic and Ghost
Fantina uses Ghost types. Ghost type moves are not very effective against Dark and Steel types. Dark and Ghost type moves are super-effective against Ghost types.
Gengar is a ghost/poison type so... ghost and dark types are super effective against ghost types. ground and psychic types are super effective against poison types
Dark is super effective against the Ghost- and Psychic-types.
physic is bad against dark