Psychic-type Pokémon are weak to Bug , Ghost , and Dark moves in the mainline games.

Core weakness answer

  • Psychic takes super-effective damage from Bug-type moves like U-turn and X-Scissor.
  • Psychic takes super-effective damage from Ghost-type moves like Shadow Ball.
  • Psychic takes super-effective damage from Dark-type moves like Crunch and Night Slash, and Dark-types are immune to Psychic attacks.

So if you’re asking “what is Psychic weak to Pokémon-wise?”, the short version is: hit Psychic-types with Bug, Ghost, or Dark attacks, and Dark-types are the safest switch-in.