He can phaze out E-killer twice with dragon tail and with SR damage added, Arceus will have lost 60 % of health in two sweeping attempts. And we are assuming it gets a free set-up here.
And for the last time, Mono-Kyogre does not resemble even a remotely close counter to offensive Groudon.
252+ Atk Life Orb Groudon Earthquake vs. 252 HP / 252+ Def Kyogre: 200-238 (49.5 - 58.91%) -- 71.09% chance to 2HKO
And about Giratina:
+2 252+ Atk Groudon Dragon Claw vs. 248 HP / 252+ Def Giratina: 272-320 (54.07 - 63.61%) -- guaranteed 2HKO
With a lum berry, Groudon gets past Giratina.