These are my Groudon's moves:

Solarbeam
Fire Blast
Earthquake
Eruption

These are my moves because since Groudon is a ground type, he is weak to water, grass, and ice(I'm pretty sure). Water can be taken with solarbeam(and because of Groudon's Drought abillity, which has the same effect as Sunny Day, solarbeam will not have to charge up). Grass and ice can be taken out with any of his fire moves. Earthquake is just a strong move(and since it is the same type as its user, it gets a 50% attack bonus)