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