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