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.
Win a match of Firefight.
Kill three or more enemies with a single grenade or explosive.
Kill an enemy after blinding them with a flashbang
Purchase your first item in the Appearance menu.
Win a match of Push.
Kill 3 enemies with a headshot in a row.
Get the first kill in a round.
Block an objective from being captured and then clear it.
Kill an enemy right after performing a speed reload.
Win a match of Checkpoint.
Kill an enemy with the last bullet of your magazine.
Kill an enemy without using weapon sights.
Successfully rig and destroy an enemy weapon cache.
Kill an enemy by shooting through something.
Kill an enemy while they are reloading.
Complete the tutorial mission.
Capture an objective as the last member of the team alive.
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 air support vehicle.
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 using the mounted weapon on a vehicle.
Kill an enemy driver with the mounted weapon of their vehicle.
Be the Most Valuable Player of a round.
Capture 100 objectives.
Call in fire support ten times as an Observer.
Kill an enemy while blinded by a flashbang
Kill an enemy while vaulting.
Kill an enemy by burning them.
Navigate through chemical gas while wearing a gas mask.