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