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