Here is the full list of all 50 Spec Ops: The Line achievements. It takes around 15-20 hours to unlock all of the achievements on Windows.
You are relieved.
Kick an enemy by vaulting over a cover. (campaign only)
Live and let die.
Complete game on "Walk on the Beach" difficulty.
Complete game on "Combat Op" difficulty.
Carry on, soldier.
The end of the line.
Kill 150 enemies with any heavy weapon. (campaign only)
Choose restraint.
Choose vengeance.
Kill 75 enemies with any shotgun. (campaign only)
Recover 12 Intel Items.
Get out of here!
Kill 250 enemies with headshots. (campaign only)
Kill 50 enemies with any sniper rifle. (campaign only)
Stand united.
Kill 100 enemies with any pistol or SMG. (campaign only)
Save a bullet.
Show mercy.
Kill an Edged Weapon Expert while he is up to 5 meters away. (campaign only)
Hit 10 enemies with your melee attack. (campaign only)
Follow your orders.
Kill an enemy by tagging him with a sticky grenade. (campaign only)
Play it loose.
Kill 350 enemies with any rifle. (campaign only)
Sprint into cover 10 times while under fire. (campaign only)
Kill 4 enemies with a shotgun in 10 seconds or less. (campaign only)
Face the horrors of war.
Engineer an exit strategy.
Kill 3 enemies with a single grenade. (campaign only)
Kill an enemy just as they are throwing a grenade. (campaign only)
Kill 5 enemies using blind fire. (campaign only)
We have contact.
Complete three chapters in a row without being killed or reloading a checkpoint.
Look out below.
What's lost is found.
Recover one Intel Item.
Kill an oryx. (campaign only)
Play it smart.
Buck the chain of command.
Complete game on "Suicide Mission" difficulty.
Kill 50 enemies with grenades. (campaign only)
Complete any chapter with 60%+ accuracy without dying or reloading a checkpoint.
Kill 50 enemies using only the Attack Command. (campaign only)
Recover all Intel Items.
Complete game on "FUBAR" difficulty.
Kill 10 enemies while they use zip lines or are rappelling. (campaign only)
Stun an enemy by dumping sand on their head. (campaign only)
Live and let live.
Blow up 10 explosive objects, killing at least one enemy each time. (campaign only)