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