>>31043667XY.
Reflection Cave.
Battle Girl Hedvig.
This is right before the game gives you Mega Evolution, so it's really the last point that Kalos can even pretend to be difficult. Battle Girl Hedvig doesn't have to pretend, though: Hawlucha is fast in general and very powerful for that point in the game, and hers had enough coverage to give anything that isn't especially bulky a hard time.
Black Belts/Battle Girls in general seem to be the only trainers who ever managed to make me lose a 'mon in Kalos after that Furfrou duo.
