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