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