So, I've been cuckoo cuckoo crazy about what to pick on my team in XY, a L74 Tyrantrum or L73 Lucario so I can defeat that Lvl 80 Mega Gardevoir at Château! Both super effective, SO WHAT?
I'll rather use Lucario on this one. Not only it is not weak againt Fairy, but can do really good damage If you Mega Evolve it. Try letting it learn Flash Cannon for with Adaptability for x2 STAB and also a Mega Stone.