I usually use the following team in double battles:
Sylveon @ Quick Claw Ability: Cute Charm EVs: 252 HP / 252 SpA / 4 SpD Modest Nature IVs: 0 Atk - Moonblast - Protect - Shadow Ball - Draining Kiss
Metagross @ Focus Sash Ability: Clear Body EVs: 252 HP / 252 Atk / 4 SpA Brave Nature - Bullet Punch - Earthquake - Psychic - Meteor Mash
Kartana @ Fightinium Z Ability: Beast Boost EVs: 252 Atk / 4 SpD / 252 Spe Jolly Nature - Leaf Blade - Sacred Sword - X-Scissor - Smart Strike
Greninja @ Waterium Z Ability: Battle Bond EVs: 4 Atk / 252 SpA / 252 Spe Hasty Nature - Hydro Pump - Ice Beam - Night Slash - Water Shuriken