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