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