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