Gardevoir @ Leftovers
EVs: 252 Sp. Attack/252 Speed/6 HP
Calm Mind - Boost your Sp. Attk and Sp. Def.
Stored Power - Powerd up by Calm Mind, and it allows you to sweep!
Psychic - Good power, STAB, and deals with Poison types.
Draining Kiss - Covers Dark types, and regain life!
Hope I helped!