A rock type move can bring his charizard and lapras down. Pikachu is no match for a ground type. A grass or electric type can take care of Blastoise, and either a flying, fire, poison, or ice type can take out Venusaur. a fighting type can bring down that snorlax.
I'd suggest these types
Fighting/Fire-Venusaur, Snorlax, lapras
Also, if you want to make pikachu easier, use covet on it, to steal its light ball. its power is halved after that, plus you get a rare item.