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