>>35618670Dragonite GX with the new Altaria seems like the way to go.
With just one Altaria and a Choice Band you 2HKO nearly everything in the format and if you get to 3 energies you can OHKO too.
The Japanese website posts deck ideas and sometimes decklist featuring all the GXs from recent sets though their format is different than ours (XY onwards)
http://www.pokemon-card.com/products/sm/sm6a.html#s1