YMUW-WWWW-WWW9-5GAF
Me up against the Super Singles Battle Chantelaine. Took freakin' forever to get here, but I finally did it and I beat her (cheating) team of all-Genies. I even managed to go 10 battles more past here before being annihilated by an Alakazam.
All my previous attempts involved some sort of tanking and slow status ailments, but these guys in the Battle Maison are cheating scoundrels so it turns out the best option is to just blast through them with the strongest physical, special, and Mega Pokemon you've got.