LogFAQs > #962353401

Light ball is an extremely poorly understood item. It doesn't actually double Pikachu's base attack stats; instead, it doubles the IV+EV boosted final attack stats of Pikachu.

So, for example, Pikachu's base SpA of 50 + Modest + Light Ball winds up being similar to a ballpark estimate of base 150 SpA. That's Kyogre's SpA level.

Raichu has a base SpA of 90. If you do the math, Raichu winds up having almost 300 base SpA, or roughly the equivalent of Kyogre using Nasty Plot. He would easily OHKO anything in the game that doesn't have extremely high SpD or other skills.

Pikachu is held back by his relatively low speed for a glass cannon (base 90) whereas Raichu has base 110, which is faster than the majority of unboosted non-legendary sweepers.

Raichu with a Light Ball would be legitimately broken.