Texas, you get a challenge that I'm probably going to give to a lot of people doing B/W.
Get an Emolga, name it
Avenger. It must be male, and have a Lonely nature. Due to the events that transpired
here it has a deep hatred of all Dark Pokemon. Whenever you encounter a Dark Pokemon, you must switch in Avenger immediately and solo it. Also, if any one of your Pokemon gets KO'd, you must switch in Avenger and solo that enemy. During either of these scenarios, you cannot use items on it, because it's
personal.
If Avenger is KO'd during any of these scenarios, it cannot battle due to heroic angst until it gets a good whack from an ally (hit by an ally in a Double/Triple battle). Also, it cannot be in a Double Battle with an ally Dark Pokemon. If somehow it has to, then it will attack the Dark Pokemon ally unless the opponents are also Dark Pokemon. During the Elite Four, it learns the meaning of friendship and teamwork, so the previous rule and the no items rule do not apply anymore.
It must know Acrobatics, and never Volt Switch until after the 8th badge, where it must know Volt Switch. It must solo Grimsley and N's Zoroark. After beating Zoroark, it's nemesis, its conscience is clear, and will help beat Ghetsis's Hydreigon as a team effort. It must be sent out against Ghetsis's Hydreigon, and use Volt Switch immediately.
Have fun!