All of the attacks in Pokémon Go are unique. Synchronoise is a charged move, so it does a large amount of damage, 80, and your Pokémon needs to charge up energy to use it, 50, specifically. Only a handful of Pokémon can learn to use it. Is the attack worth it for it?
Synchronoise is a Psychic-type attack. It will be effective against Fighting and Poison-type Pokémon, but it’s not good when fighting Dark, Psychic, and Steel-type Pokémon.
These are all of the Pokémon that can learn Synchronoise in Pokémon Go.
It all comes down to what movesets each of these Pokémon has at their disposal. For Golduck, it’s the weakest of the three. You’re going to be using it in PvE, probably against three-star raids. Unfortunately, Golduck has better options available to it, such as cross chop and ice beam. You can toss Synchronoise out for Golduck.
Gallade is in the same boat as Golduck, but it’s much stronger. You’ll regularly see Gallade battling in the Master League, and it’s a risky choice given its low stamina and defense stats. It makes up for those low stat numbers by having a large amount of attack. Gallade has several better moves that it can use that don’t require as much energy as Synchronoise.
The final Pokémon, Gardevoir, will get the most use of it. Synchronoise requires less energy than other options available to it. Plus, Gardevoir is a Fairy and Psychic-type Pokémon, meaning it will receive a same attack type bonus (STAB) with this move, dealing more damage. It’s on the same spectrum as Gallade, where it has a higher attack stat, but lower defense and stamina. You want to lean on Gardevoir’s STAB moves as much as possible.
Overall, Synchronoise is an okay attack. If you want to give Gardevoir the best moveset, make sure one of its charged moves is Synchronoise. Other than Gardevoir, no other Pokémon that can use this attack benefits it from that much.