From Bulbapedia, the community-driven Pokémon encyclopedia.
Raymond (Japanese: レイモンド Raymond) is a Pokémon Trainer Ash battled in Mewtwo Strikes Back.
While Ash and his friends were waiting to eat, he approached them and asked Ash for a battle. Although he claimed he was too weak to work, Ash immediately jumped up, ready for battle (though in the Japanese version, he stated that he was just going to have a quick battle before lunch).
However, despite Raymond's eagerness, Ash successfully knocked out all five of his Pokémon in rapid succession. In fact, Pikachu took out three of the Trainer's Pokémon in one Thunderbolt. The Trainer was stunned by the defeat, and has not been seen since his brief appearance.
Notably, Raymond had a then-unknown Generation II Pokémon when he appeared: a Donphan.