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