poison
I assume that you are referring to Fighting-Type Pokémon. When attacking, they are weak against Poison-Types, Flying-Types, Bug-Types, and Psychic-Types, and ineffective against Ghost-Types. When defending, they are weak against Flying-Types and Psychic-Types.
Natu is a Psychic and Flying type Pokemon it is weak against Electric types, Rock types, Ghost types and Dark types.
Fairy types are weak against Poison and Steel types, and their attacks aren't very effective against them or Fire types.
Strong ground and psychic Pokemon such as Claydol, Metagross, and Tyranitar. Both ground and psychic moves are super-effective against poison. They are both multiplied by 2. A good ground type move is earthquake, but since many poison Pokemon have levitate or are flying, they can avoid this. It depends on dual types, abilities, available moves, etc., of both Pokemon, but the strongest Pokemon against poison Pokemon generally would be the strongest psychic and ground Pokemon. Some excellent psychic and ground Pokemon (strongest is quite subjective, so there's no definite answer) are Metagross and Tyranitar, respectively. Claydol is a strong Psychic and Ground dual-type Pokemon.
Elite Four Lucian SquadMr. Mime male Lv.59 Psychic weak against DARK, BugMedicham male Lv.60 Fighting/Psychic weak against FLYING, GhostGirafarig male Lv.59 Normal/Psychic weak against DARK,BugAlakazam male Lv.60 Psychic weak against DARK,BugBronzong Lv.63 Steel/Psychic weak against FIRE, Ground yea but on platnium after mr.mime there is espeon lvl55 use dark on espeondont use flying types
Psychic and Ghost
Psychic and flying types are super effective against fighting types.
Bug, ghost, and dark types are most effective against psychic types.
the flying type is super effective against fighting. also psychic type moves are super effectiveFighting-types are weak against Psychic, Fairy, and Flying-type attacks.
They are super effective against Grass, Dark and Psychic types.
Dark is super effective against the Ghost- and Psychic-types.
Rock, electric, ice, and psychic types are super effective against Crobat.
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.
Fighting types are weak against psychic and flying types.
Weakness as in types? Like psychic moves aren't effective on a certain type? Well, psychic has no effect on dark-types, not very effective on psychic-types (DUR), and not very effective on steel-types. Although, if you were wondering what psychic will LOSE against, (as in super effective types that damage psychics greatly), the the types would be dark-types, bug-types, and ghost-types. Hope I helped! :)
Psychic Pokemon are Super effective by Bug type, Dark type and Ghost types
Psychic types are super effective against Poison types.