Raisins on a Rampage is a side mission in South Park: The Fractured But Whole.
Plot details follow.
Defeat 15 Raisins Girls.
This mission comes early on in the game. It is one of the simpler side quests in South Park. After obtaining Mosquito, he will be revealed to be hunted throughout the town. Mosquito will ask for your assistance to get them off his back. You will need to defeat 15 Raisins girls. You can fight these foes whenever you like.
Completing this mission opens up the A Perky Predicament side quest.