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