For Bulky DD.
I recommend running 208 attack with an Adamant nature.
+1 208+ Atk Tough Claws Mega Charizard X Drgon Claw vs. 0 HP / 0 Def Keldeo: 303-357 (93.8 - 110.5%) -- guaranteed OHKO after Stealth Rock
Since I run a bulky DD set for Char X in my team, I have ran into this problem a LOT of times, actually, Jolly max attack cannot OHKO Keldeo either. Not OHKO-ing means:
252 SpA Choice Specs Keldeo Hydro Pump vs. 4 HP / 0 SpD Mega Charizard X: 306-361 (102.6 - 121.1%) -- guaranteed OHKO
252 SpA Choice Specs Keldeo Hydro Pump vs. 248 HP / 0 SpD Mega Charizard X: 306-361 (85.2 - 100.5%) -- 6.3% chance to OHKO
The slightest damage after this can kill you.
As for me, I run 68 Spe, just enough to outspeed Greninja at +1, 232 HP / 208+ Atk / 68 Spe is my set. Bulky and powerful, but fast only after DD.
I recommend running 208 attack with an Adamant nature.
+1 208+ Atk Tough Claws Mega Charizard X Drgon Claw vs. 0 HP / 0 Def Keldeo: 303-357 (93.8 - 110.5%) -- guaranteed OHKO after Stealth Rock
Since I run a bulky DD set for Char X in my team, I have ran into this problem a LOT of times, actually, Jolly max attack cannot OHKO Keldeo either. Not OHKO-ing means:
252 SpA Choice Specs Keldeo Hydro Pump vs. 4 HP / 0 SpD Mega Charizard X: 306-361 (102.6 - 121.1%) -- guaranteed OHKO
252 SpA Choice Specs Keldeo Hydro Pump vs. 248 HP / 0 SpD Mega Charizard X: 306-361 (85.2 - 100.5%) -- 6.3% chance to OHKO
The slightest damage after this can kill you.
As for me, I run 68 Spe, just enough to outspeed Greninja at +1, 232 HP / 208+ Atk / 68 Spe is my set. Bulky and powerful, but fast only after DD.