Here is the full list of all 17 GIGABUSTER achievements.
Complete the opening stage.
Beat Bjorn without letting his fangirls reach him.
Beat Bee without using a ranged attack.
Beat Lucy without using a ranged attack.
Beat Roach without jumping.
Beat Zipplin without getting hit.
Beat Su-Z without using a ranged attack.
Complete the oil rig's elevator section without touching the elevator.
Complete the Astrominer stage without touching a tractor beam's UFO.
Don't touch an ice cream block in the ice cream factory.
Complete the Practice hospital stage without destroying a skull.
Complete HQ1 without getting hit.
Complete HQ2 without getting hit.
Complete HQ3 without getting hit.
Defeat Happiness.
Complete boss rush mode.
Complete the second city stage.