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.
Completed the game on Hard.
Completed the game with a secret character.
Was defeated in detention.
Reached Max Level.
Reach 100% completion.
Enter the Penthouse.
Collected $5000
Defeated an enemy with a fish.
Catch a boomerang.
Parry 10 enemy attacks.
Completed all of Godai's quests.
Destroyed all Sabu statues.
K.O. Abobo.
K.O. Noize.
K.O. Sabuko.
K.O. the secret boss.
Find the keys in the junk yard.
Obtain an item from the Pawn Shop.
K.O. Hibari.
Enter the Mall.
K.O. Yamada.
Defeated an enemy by hitting them with another enemy.
K.O. Misuzu.
Attacked Mr. Rudis.
Destroy a vending machine.
Equip a new outfit.