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