Thunderbolt: Thunderbolt is a powerful Electric-type move that is also super effective against Gyarados. It has a base power of 90 and a 10% chance to paralyze the target, which can further hinder Gyarados's ability to battle.
Earthquake: Earthquake is a powerful Ground-type move that is not super effective against Gyarados, but it can still deal significant damage. It has a base power of 100 and a 10% chance to cause the target to flinch, giving you an opportunity to follow up with another attack.
Stone Edge: Stone Edge is a powerful Rock-type move that is not super effective against Gyarados, but it can still deal significant damage. It has a base power of 100 and a 30% chance to cause the target to flinch, giving you an opportunity to follow up with another attack.
It's important to note that the effectiveness of these moves may vary depending on the specific Gyarados you are facing, as Gyarados can have different abilities and stat spreads. Additionally, your own Pokémon's stats, abilities, and moves will also play a role in the outcome of the battle.