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