Salamence is a Dragon and Flying-type and because of which its weaknesses are Rock, Ice and Dragon prior to Pokemon X and Y however Fairy-types were added as a weakness for Salamence as of X and Y.
Being a dragon/flying type, like dragonite, Salamence is 4 times weak against Ice type moves. Dragon type moves are also super-effective but only by x2.
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.
Rock, electric, ice, and psychic types are super effective against Crobat.
Steel is super effective against rock type pokemon.
Salamence is weak against Ice (4x the damage), Fairy, Rock, and Dragon-type attacks.
Any Pokemon that knows a rock, dragon, or ice move. Those are the things Salamence is super effective against.
Being a dragon/flying type, like dragonite, Salamence is 4 times weak against Ice type moves. Dragon type moves are also super-effective but only by x2.
Flying and Psychic are super effective against fighting
Lightning is super effective against Water and Flying types in Pokémon battles.
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.
super effective is bug
psychic pokemons and attacks are super effective
Bug Type and Fighting Type moves are super effective against it.
Steel is super effective against rock type pokemon.
Rock, electric, ice, and psychic types are super effective against Crobat.