Slakoth's best moveset in Pokémon GO is Yawn and Body Slam, with 4.75 damage per second, and it can deal 59.9 damage before Slakoth faints. This is true when battling in neutral weather.
All Slakoth movesets ranked
Here is a complete list of Slakoth movesets in Pokémon GO, ranked by their DPS and TDO. You can change the weather and the opposing Pokémon.