Kyogre Groudon or Rayquaza

[Azonic]

Kyogre IMO. I don't think it's OHKO'd by Rayquaza so Kyogre fights back with Ice Beam and... yah.

depends does it learn Ice Beam

No, I'm sure the king of the sea does not learn Ice Beam.

 

[True Reign]

Rayquaza wins because it's a dragon and since it has a better movepool than the other two legendaries.

 

[Apathetic_Yen]

Rayquaza Lvl 100 Holding Magnet Nature that Boosts Sp Att Max Calcuim used use Thunder Crtical Hit should take care of Kyogre then ill use Blizzard on Groudon then Rayquaza should win

Um...yeah, if ALL of those reasons just so happen to take place, INCLUDING the critical hit. Other than that:

Kyogre can take a hit from Thunder and a Solarbeam that's been boosted by Sunny Day easily and take out Rayquaza and Groudon with Ice Beam/Blizzard, or Surf if there is no sunny day. Hell Rayquaza would probably be better off using Outrage instead