Serperior (M) @ Leftovers
EVs: 252 Atk / 160 Def / 96 Spd
Adamant Nature (+Atk, -SAtk)
- Leaf Blade
- Dragon Tail
It outspeeds Swampert, being able to immediatly set up Coil, Can use taunt to avoid any cursing, Has Leaf Blade as a hard hitting attacking move.
And last but not least, Serperior is UU or NU one without Contrary last I checked.