Here is the full list of all 29 River City Girls achievements. It takes around 10-12 hours to unlock all of the achievements on Windows.
That wasn't very nice!
Catch a dodgeball thrown by your ally.
Complete the game in Co-Op.
Reached Max Level.
Reach 100% completion.
Completed the game with a secret character.
Defeated an enemy with a fish.
Completed all of Godai's quests.
Completed the game on Hard.
Was defeated in detention.
Destroyed all Sabu statues.
K.O. the secret boss.
Attacked Mr. Rudis.
Enter the Mall.
Obtain an item from the Pawn Shop.
Find the keys in the junk yard.
Enter the Penthouse.
Destroy a vending machine.
Collected $5000
Catch a boomerang.
Defeated an enemy by hitting them with another enemy.
Parry 10 enemy attacks.
Equip a new outfit.
K.O. Misuzu.
K.O. Yamada.
K.O. Hibari.
K.O. Abobo.
K.O. Noize.
K.O. Sabuko.