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