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