Hmmm...
I somehow beat the elite four with all of my pokemon below level 50 and then Ghetsis with them still being below 50?
Wait, that's actually pretty smart instead of stupid isn't it? :P
Oh! I've got something now. The psychic elite four trainer, Caitlin. I put my Zoroark in the front and my Virizion in the back, then amped up my Zoroark's special attack to the max with Nasty Plot while her pokemon kept trying to use Psychic on me, which did absolutely nothing of course. Then I 1-hit ko'ed all of her pokemon with night daze. xD
The really stupid part though is when she sent out her sigiliph and I thought I could use nasty plot one more time, but she used air slash, which she thought would be super effective, and it was a critical hit and knocked my Zoroark out instantly. -_-