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