That's insane I can't believe that's possible. Wait, is that Primal Groudon holding an item that isn't a Red Orb? That can't happen in game, (Can it? I don't know if Ditto would work.) but I can fix this. If a Kecleon used Skill Swap on Deoxys-A to allow it to change its type before Pure Power was Skill Swapped onto it then this amount of overkill could happen in game. Don't have access to a Deoxys on a Gen III to teach it Mimic? Use a V-create Mega Rayquaza and show people why we banned him from Ubers. Also, I think you forgot to Skill Swap Dry Skin onto that Ghastly, not that it needs to be any more dead.
As for beating that amount of annihilation, I think that a fifth turn Ice Ball against a Dragon/Flying/Grass Ghastly should be more powerful. Salamence gets Defense Curl to boost the power farther, and despite his lower Attack, he could be more powerful than Mega-ICanDealOverABillionPercentDamage-Raquaza using the same move.
One last note, are Critical Hits applied for these calculations? If not, I want to see Crits! Death to Ghastly! >:D