Here is the full list of all 32 Bamerang achievements.
Pick up 100 points
Throw someone off the platform
Hit a boomerang mid-air with your boomerang
Fall from the platform and get picked up by the goddess
Hit two players at once
Hit a player with a fully charged boomerang that flew a full curve
Land the first hit
Throw the first boomerang
Play your first match
Play 10 matches
Play 50 matches
Play 100 matches
Pick up 1000 points
Pick up 10000 points
Throw 50 boomerangs
Throw 250 boomerangs
Throw 1250 boomerangs
Land 20 hits
Land 100 hits
Land 500 hits
Hit three players at once
Hit each other at the same time
Throw 10 players off the platform
Throw 30 players off the platform
Throw 100 players off the platform
Catch a boomerang of your opponent
Catch 5 boomerangs of your opponents
Catch 20 boomerangs of your opponents
Catch 99 boomerangs of your opponents
Play 5 unique maps
Play 10 unique maps
Play 25 unique maps