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