THE FINAL BATTLE
Attack!
Well, the bad news is that Gardevoir's faster than Scizor. You've committed that to memory after facing your rival in the past.
The good news is that Bullet Punch is faster than Gardevoir, which is why you taught it to him. It's a weak move to balance that out, but with the Technician ability, Scizor's Life Orb, AND Gardevoir's weakness to Steel, there's no way she's walking away from it.
Scizor strikes before Gardevoir can even react. It takes out the last of Gardevoir's energy, and she goes down easily. The Life Orb's recoil takes its minor toll, the first scratch Scizor's taken this whole battle.
Five-on-five now. The playing field's been leveled, and your rival doesn't seem to mind. Her next Pokémon ends up being the Ghost/Fire Chandelure.
Oh lord. Chandelure WILL be a problem for Scizor, and he WILL NOT survive even a single hit from a type he's double-weak to. Nothing he knows can even put a dent in that thing before that happens. You have to switch.
You can go for good old Greninja since each of his types counters one of Chandelure's, though that will change depending on what he uses due to Protean. Alternately, you can just go balls-to-the-wall crazy and throw out your Lunala-shaped nuke.