Cliff is one of three Team GO leaders players will battle in Pokémon Go. To beat him, you’ll have to defeat Pokémon like Aerodactyl, Slowking, and Dusknoir.
Aerodactyl is a Rock and Flying-type Pokémon, which means it will be weak against Water and Ice-type moves. But it will also suffer greater damage from Rock, Steel, and Electric-type attacks.
It will be the first Pokémon you’ll face when battling against Cliff, so make sure you bring Pokémon such as Mamoswine with Powder Snow and Avalanche to quickly and effectively faint Aerodactyl.
Other Pokémon you can use are Metagross, Blastoise, Electivire, Kabutops, Aggron, or Politoed considering the high effective damage they can deal to Cliff’s Aerodactyl. But any Pokémon that knows Water, Ice, Rock, Steel, or Electric-type moves will give you an advantage.
This is also valid for when Aerodactyl is featured in raids. But when it comes to Cliff’s battle, you’ll have to keep in mind his next Pokémon in the lineup when choosing your party.
The second Pokémon he uses can be Gallade, Slowking, or Cradily. After you beat one of those, the third Pokémon can be Tyranitar, Dusknoir, or Mamoswine.