As long as the number of Pokémon in play (both yours and your opponent's) that has Team Magma in its name is 3 or less, Team Magma's Groudon can't attack.

Choose 1 of your opponent's Pokémon. This attack does 20 damage to that Pokémon. (Don't apply Weakness and Resistance for Benched Pokémon.)

If the Defending Pokémon already has at least 2 damage counters on it, this attack does 50 damage plus 20 more damage.