Shadow Kakuna's best moveset in Pokémon GO is Poison Sting and Struggle, with 3.22 damage per second, and it can deal 24.0 damage before Shadow Kakuna faints. This is true when battling in neutral weather.
All Shadow Kakuna movesets ranked
Here is a complete list of Shadow Kakuna movesets in Pokémon GO, ranked by their DPS and TDO. You can change the weather and the opposing Pokémon.