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