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