It doesn't need any Attack EVs if it wants to 2HKO the standard WishBliss set. All it needs is an Adamant nature.
347 Atk vs 119 Def & 651 HP (100 Base Power): 418 - 492 (64.21% - 75.58%)
If you want to OHKO it, you need 252 Attack EVs and a Life Orb.
416 Atk vs 119 Def & 651 HP (100 Base Power): 650 - 766 (99.85% - 117.67%)
What if he's Impish?