Here is the full list of all 13 Boomerang Fu achievements. It takes around 2-3 hours to unlock all of the achievements on Windows.
Being on time to things
Shattered a lot of frozen enemies
Killed opponents while unarmed
One of your "teammates" killed you
Spent a lot of time hiding in the bushes
Squishing several opponents with moving blocks
Killed many opponents with the telekinesis powerup
Telefragged an opponent
Regularly killed yourself with the explosive boomerang
Killed a lot of enemies with fire
Killed an opponent after dying
Dodged a lot of boomerangs
Mastered the disguise powerup