Here is the full list of all 48 River City Ransom: Underground achievements.
Interrupt all bosses in the flashback sequence.
Earn Ribbon Finder. You're the best around!
Earn one ribbon. You did it!
Keep an enemy airborne for at least seven seconds.
Fist bump 10 times during a combo.
Collect all 6 dog tags by beating backers with special moves.
Hit a baseball back and forth with a bat 9 times in a row.
Be denied 100 fist bumps.
Grab a weapon thrown at you.
Collect $500 total
Grab a weapon thrown at you and throw it back to kill enemy who threw it at you.
Buy everything at least once.
Fight every enemy.
Find all the Hidden Books.
Climb 10 minutes worth of fences.
Don't take any damage in 5 subway train rides.
Whip an animal.
Complete a character's moves list.
Come back from a last chance 20 times.
Beat every boss without taking damage.
Defeat 100 nerds using projectiles.
Defeat 100 Agent Clones.
Complete the flashback sequence without taking any damage.
Find and defeat all Abobo variations (white,black, green, purple).
Play through a level with friendly fire on, without hitting anyone.
Drink 25 of each kind of soda.
Buy or find all hideout swag.
Die in a pit 50 times.
Defeat PROTO using only moves he uses against you.
Punch every coin-giving object in the game.
Make a stack of 10 objects.
Find every boss' dialogue lines.
Barf with Mike and Provie 20 times each.
Beat the game as every hero.
Hit 30 "home runs."
Complete the flashback as both heroes.
Defeat 10 enemies with snowballs.
See every bum.
Fall in a pit 30 times.
Die 100 times.
Eat an octopus roll in front of the octopus.
Interrupt all bravo squad members during their salutes.
Stun 5 enemies with poop.
Sink 5 basketballs.
Sink 5 dodgeballs.
Hit Heavy Bag 200 times.
Earn $100 in Flashback Mode.
Buy 10 group saunas.