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