Go to this website:
http://www.serebii.net/pokedex-dp/psychic.shtml
Here is a list of all the Psychic type pokemon. Abra Kadabra Alakazam ralts kirlia gardevoir Lunatone Solrock Mr.Mime Mime.jr bronzor bronzong espeon Chimecho chingiling
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 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.
Here is a list of all pokemon that can learn Psychic: http://www.serebii.net/attackdex/psychic.shtml
Psychic. Although all types of attacks excep normal attacks affect a ghost pokemon but psychic is most effective.
Bug, Ghost, and Dark type moves are all super effective against Psychic-type Pokemon. As these are considered basic fears of the mind and would be the weakness of a Psychic which fights using its mind.
dark, bug, and ghost are all super effective against psychic type pokemon.
every game has the same types and weaknesses. as usual psychic is weak to bug and dark type Pokemon in all games, not just Pokemon platinum.it's also weak to ghost
Machamp is a fighting type Pokemon all fighting Pokemon are weak against flying types and psychic types that use flying type and psychic type moves so Pokemon like pidgeot or alakazam will do good against machamp.
Bug, Ghost, and Dark type moves are all super effective against Psychic-type Pokemon. As these are considered basic fears of the mind and would be the weakness of a Psychic which fights using its mind.
Well, you don't NEED a water type at all. I went through Pokemon Emerald with a Torchic/Combuskin/Blaziken (and possibly an Azurill) but possibly a Dark type Pokemon because they are super affective against Psychic type Pokemon. NOT a Poison type Pokemon because Psychic type Pokemon are super effective against Poison type Pokemon. I REALLY hope that this answers your question!!! :-)
I know it's weak to Dark type, and I think it's weak to Ghost type but I'm not sure.