This may be cheap, but I'm not about to sit idly by and watch Sparky's health get sapped by offensives, toxins, AND a Leech Seed...

Use Toxic when he comes in for a Body Slam. Then, whip up a 3% Substitute to (barely) absorb the Leech Seed and the Solarbeam. Finish by taking advantage of the sunny weather yourself: Wait for the Solarbeam to fly past, then blast him with another Fire Punch!

Move: Toxic, Substitute (3%), Fire Punch