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