That demon insect that won't be killed no matter how many times you hit it with your shoe

Vivillon @ Focus Sash | Compoundeyes | Timid
-> Sleep Powder
-> Quiver Dance
-> Bug Buzz
-> Hurricane

Vivillon - the butterfly with quite a few stylish formes, none of which actually do anything outside of looking pretty.

But this butterfly is actually a pretty good set-up sweeper, if a little weak to priority, because Sleep Powder & Hurricane are boosted to >90% accuracy thanks to Compoundeyes. Quiver Dance is mainly used to boost Speed and Special Attack, as you'll quite often be on 1 HP when setting up, so the Special Defence boost isn't that helpful. Vivillon is quite a good pokemon despite this, and wields the power to destroy unprepared teams (lacking Scizor, Lucario, Dragonite, Azumarill... Yeah, it's not that great)