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