With solar beam, Groudon does fairly well against Kyogre with thunder (as thunder does half damage to Groudon). It's weak, however, to both hydro pump and blizzard, and waterfall (Kyogre's only quick move) will steadily take chunks out of Groudon's HP. Therefore, it wouldn't hurt to slot it in against a Kyogre with thunder, but that's about it.
GamePress
Groudon vs kyogre
According to pokebattler, groudon with solar beam is my top three against kyogre of unknown moveset. However, in game press it is not even mentioned as good counter. I know it's not that good vs hydropump kyogre, but otherwise it should be fine.
What do you think?
