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