Don't use 252 Atk / 252 SpA. Use 252 SpA / 252 Spe instead, as its Phy Atk is naturally high. And, Mild is better than Adamant. Flamethrower is a subpar choice, consider Fire Blast as it picks more KOes or something like Eruption.
@FlyinSquirl PDon doesn't need physical Fire-STAB. Special Fire STAB breaks Groundceus, which is one of its check so that's better.
@~TastyMushroom~ ):< Heat Crash is bad because it can't hit Dynamaxed Pokemon. Anyways, Fire Blast / Eruption >>> Heat Crash / Fire Punch whatever it gets