You should used bug, ghost, and dark type pokemon.
Chat with our AI personalities
you should use either ground or psychic Pokemon
Psychic type Pokemon are weak to Dark, Bug and Ghost type moves. Psychic Pokemon can also struggle against Steel types as not all Psychic Pokemon can learn moves effective against them. Overall the best type to use against Psychic types is the Dark type. Since the Dark type is not only super effective against them but is also immune to Psychic moves.
Machamp is a fighting type Pokemon all fighting Pokemon are weak against flying types and psychic types that use flying type and psychic type moves so Pokemon like pidgeot or alakazam will do good against machamp.
Grass moves are neither supper effice on not effictive its better to use a psychic to fight a fighting pokemon
Psychic, Ghost and Dark type Pokémon. Gastly is also strong against itself, if you teach it a move like Shadow Ball. Otherwise get Mewtwo or Alakazam to use their powerful Psychic attack.