What about Regigigas and Shuckle?
Regigigas @ Assault Vest
Trait: Slow Start
EVs: 252 Atk / 200 HP / 52 Spe
Adamant Nature (+ Atk, - SpA)
- Drain Punch
- Ice Punch
- Zen Headbutt
- Knock-Off
Shuckle @ Leftovers
Trait: Sturdy
EVs: 252 Def / 252 SpD / 4 HP
Impish Nature (+Def, - SpA)
- Sticky Web
- Gastro Acid
- Guard Split
- Stealth Rock / Toxic
Basically, you supress Regigigas' ability first turn. Next turn, while hitting hard with Regigigas, use Guard Split, which makes the Regi really bulky, especially with Assault Vest. He himself can regain health by using Drain Punch, otherwise he just deals massive damage. Shuckle is now there for trolling and will probably die soon because of the weakend Def.