A fire type like Magmar or Charmander. Any rock move, Ice move, Fire move, Flying move, Electric move.
A Dark or Bug Type Pokémon like Umbreon, Murkrow, Butterfree and Beautifly for some examples would be super effective against Unown since Unown is a Psychic Type Pokémon.
The dark type is super effective against it, plus psychic can't hurt them, and the bug type is super effective, but it takes psychic attacks as a normal effective hit. I would suggest using beautifly or kricketune, since there isn't any murkrow in Pearl.
Flying and Psychic are super effective against fighting
Lightning is super effective against water. I hope this helps.
Ghost & Flying. I believe that's it! Not dark or bug because although they're super-effective against Psychic, they are not-effective against Fighting. And not Psychic, because though it's super-effective against Fighting, it's not-effective against Psychic.
Water and Grass attacks are super effective against Onix.
psychic pokemons and attacks are super effective
super effective is bug
Bug Type and Fighting Type moves are super effective against it.
Rock, electric, ice, and psychic types are super effective against Crobat.
Steel is super effective against rock type pokemon.
Bug types are super effective against Dark, Grass and Psychic (x2) in Generation II-onward. In Generation I, they were super effective against Grass, Poison and Psychic.