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