>>23502012He out hits Mega Swampert by a decent margin already, even at Jolly.
>252+ Atk Mega Swampert Waterfall vs. 0 HP / 0 Def Snorlax: 228-268 (49.4 - 58.1%) -- 97.7% chance to 2HKOBest case scenario would probably be about 55 into attack, 25 or 30 into speed, and the rest in Special Defense. Ability could be Tough Claws or Moxie, but you know Gamefreak will give it Strong Jaw.