Here is the full list of all 35 Colony Assault achievements.
Survive an explosion
Personally shoot 1000 aliens
Over 100 000 aliens killed globally
Finish episode 1 on any difficulty
Finish episode 1 on nightmare
Finish episode 2 on any difficulty
Finish episode 2 on nightmare to unlock nightmare++
Finish survival mod
Survive an alien attack
Kill an airborn alien
Survive 15 vawes in survival mod
Activate the nuke and escape - survival mod
Find the alien artifact in episode 2
Extract 75 civilians in one game
Finish episode 2 without personally shooting a single alien
Finish episode 2 personally killing at least 10 aliens and personally liberating at least one civilian
Kill 25 aliens in a row using a sniper rifle without missing a single shot - survival mod
Kill 8 aliens in a row using a shotgun without reloading
Burn 100 aliens using a flamethrower
Kill 100 aliens using grenades or grenade launcher - survival mod
Kill 10 aliens using a minigun in one full burst
Kill 100 aliens using a bladed weapon - survival mod
Traverse 33% of the sector driving the APC without stopping
Kill alien princess with a bladed weapon
Force 100 aliens into abyss
Drive over 100 aliens