252 Atk Tough Claws Mega Charizard X Flare Blitz vs. 172 HP / 0 Def Azumarill: 153-181 (39.8 - 47.1%) -- 46.9% chance to 2HKO after Stealth Rock (153*, 156, 157, 159, 161, 162, 165, 166, 168, 170, 171, 174, 175, 177, 179, 181)
+1 252 Atk Tough Claws Mega Charizard X Flare Blitz vs. 172 HP / 0 Def Azumarill: 229-270 (59.6 - 70.3%) -- guaranteed 2HKO
+2 252 Atk Tough Claws Mega Charizard X Flare Blitz vs. 172 HP / 0 Def Azumarill: 306-361 (79.6 - 94%) -- 50% chance to OHKO after Stealth Rock
252+ Atk Choice Band Huge Power Azumarill Play Rough vs. 0 HP / 0 Def Mega Charizard X: 246-289 (82.8 - 97.3%) -- guaranteed 2HKO
(246*, 247, 250, 253, 256, 259, 262, 265, 268, 271, 274, 277, 280, 283, 286, 289)
* On minimum rolls, M-ZardX loses 51HP due to FB recoil and Azumarill attacks it for 246HP more:
246 + 51 = 297, which is exactly the same amount of HP M-ZardX has without any HP or Def investment (if the 4 remaining EVs were placed into Def instead of SpD, then the KO wouldn't be guaranteed, but Azumarill would still have a great chance to KO it anyway).