Here is my drawing of a cutscene will initiate where Groudon pounds over Kyogre onto the pit, resulting in the fight being against Groudon and Rayquaza instead of Kyogre and Rayquaza. Defeating the pair in under a minute and completing the rest of Adventure Mode with no continues will result in getting the chance to unlock Groudon. Yeah, that's from Wii fanon game called "Super Smash Bros. Pokemon Edition". That's why Groudon disliked rain.

Groudon and Kyogre belongs to Game Freak and The Pokemon Company

A request for Hiro-Hamada-Rockz