Here is the full list of all 35 Insurgency: Sandstorm achievements. It takes around 20-25 hours to unlock all of the achievements on Windows.
Call in fire support ten times as an Observer.
Destroy an enemy air support vehicle.
Capture 100 objectives.
Kill 3 enemies with a headshot in a row.
Kill an enemy using the mounted weapon on a vehicle.
Get the first kill in a round.
Successfully rig and destroy an enemy weapon cache.
Kill an enemy after blinding them with a flashbang
Kill three or more enemies with a single grenade or explosive.
Block an objective from being captured and then clear it.
Capture an objective as the last member of the team alive.
Kill an enemy with the last bullet of your magazine.
Kill an enemy while they are reloading.
Win a match of Checkpoint.
Kill an enemy without using weapon sights.
Kill an enemy by burning them.
Kill an enemy right after performing a speed reload.
Kill an enemy by shooting through something.
Purchase your first item in the Appearance menu.
Complete the tutorial mission.
Destroy an enemy weapon cache using a remote explosive charge.
Kill an enemy with an enemy's live grenade.
As a Commander, kill an enemy using fire support.
Kill an enemy with a knife.
Kill an enemy by bashing in a door.
Destroy an enemy vehicle with a mine.
Drive a vehicle full of teammates for more than 15 seconds.
Kill an enemy with a vehicle.
Kill an enemy driver with the mounted weapon of their vehicle.
Win a match of Firefight.
Win a match of Push.
Be the Most Valuable Player of a round.
Kill an enemy while blinded by a flashbang
Kill an enemy while vaulting.
Navigate through chemical gas while wearing a gas mask.