Psychic Pokemon, as well as in any other Pokemon game are weak to the types; Bug, Dark, and Ghost. However, Psychic has no effect at all on Dark Pokemon.
psychic type pokemon are weak against psychic steel and dark
What are psychic type Pokemon weak against
Latios is a dragon and psychic type of Pokemon. In Pokemon Sapphire, you can find him roaming around in random locations.
Fighting types are weak against psychic and flying types.
In Pokemon Sapphire, Ruby and Emerald the 7th Gym that's located in Mossdeep City has Psychic type 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.
Pokémon types that can beat Psychic-type Pokémon are Dark, and Bug. Ghosts however lose against Psychic.
Bug, Ghost, and Dark type are super-effective (2x) against Psychic type Pokemon (assuming it is pure Psychic, such as a Mew)
The fire type is not super-effective, not very effective or ineffective against the psychic type. Fire type moves deal unmodified damage to psychic type pokemon.
Fighting-type pokemon are weak against it.
Jirachi is a legendary Steel and Psychic type Pokemon. It does not occur naturally in Pokemon Sapphire, and can only be obtained through official Nintendo events.
Bug, Ghost, and Dark type are super-effective (2x) against Psychic type Pokemon (assuming it is pure Psychic, such as a Mew)