Okay, here's my suggestion:


Landorus (M) @ Choice Scarf
Trait: Sand Force
EVs: 252 Atk / 4 SAtk / 252 Spd
Naive Nature (+Spd, -SDef)
- Earthquake
- Stone Edge
- U-turn
- Grass Knot
Big bad Landorus. Landorus can take care of both Rayquaza and Groudon with Stone Edge and Grass Knot respectively (Grass Knot only tops at 68.29% unfortunately, but we have Lugia too), and can check Zekrom with its Ground typing. It's faster than Rayquaza and since it doesn't have ExtremeSpeed you can just Stone Edge it to death. Landorus also checks Mewtwo and Deoxys-A in case team 1 chooses them with its high Speed, U-turn, and Earthquake. This Landorus also takes full abuse of sandstorm thanks to its Sand Force ability which boosts Earthquake and Stone Edge. There really isn't anything else to say, as that's fairly straightforward...