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.
Dodged a lot of boomerangs
Killed opponents while unarmed
Being on time to things
Shattered a lot of frozen enemies
Killed a lot of enemies with fire
Mastered the disguise powerup
Killed an opponent after dying
Regularly killed yourself with the explosive boomerang
One of your "teammates" killed you
Killed many opponents with the telekinesis powerup
Spent a lot of time hiding in the bushes
Telefragged an opponent
Squishing several opponents with moving blocks