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