[quote=monstahunta]
Catch a Caterpie, and evolve it into Butterfree. Make sure to keep the powder attacks when it learns them.
[/quote]

I usually go for powerful attacks rather than status effects and stat reductions/buffs. I'll likely have a monster that can put someone to sleep later though, for easy legendary catching... not sure about butterfree though. Parasect and it's false swipe and spores have always suited me well for that kind of thing.