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