Try this team:

Rayquaza:Outrage - Fly - Hyperbeam - Solarbeam.
Blaziken:Sky uppercut - doublekick - blazekick -overheat.
Gengar:Confuse ray - Shadow punch - dream eater - shadow ball.
Kyogre:Surf - Hydro pump - double edge - sheer cold.
Groudon:Flamethrower - fire blast - fissure - solarbeam.
Mewtwo:Thunder - fire blast - blizzard - psychic.

I have never lost!