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.
Follow your orders.
Play it loose.
Choose restraint.
Kill 75 enemies with any shotgun. (campaign only)
Kill 50 enemies with grenades. (campaign only)
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.
Kill 150 enemies with any heavy weapon. (campaign only)
Kill 10 enemies while they use zip lines or are rappelling. (campaign only)
Stun an enemy by dumping sand on their head. (campaign only)
You are relieved.
Live and let live.
Live and let die.
Complete game on "Walk on the Beach" difficulty.
Complete game on "Combat Op" difficulty.
Complete game on "Suicide Mission" difficulty.
Carry on, soldier.
Recover all Intel Items.
The end of the line.
Choose vengeance.
Get out of here!
Kill 250 enemies with headshots. (campaign only)
Blow up 10 explosive objects, killing at least one enemy each time. (campaign only)
Stand united.
Kill 50 enemies with any sniper rifle. (campaign only)
Kill 100 enemies with any pistol or SMG. (campaign only)
Kill an oryx. (campaign only)
Show mercy.
Save a bullet.
Kill an Edged Weapon Expert while he is up to 5 meters away. (campaign only)
Kill 3 enemies with a single grenade. (campaign only)
Kill 350 enemies with any rifle. (campaign only)
Kill an enemy by tagging him with a sticky grenade. (campaign only)
Kill 50 enemies using only the Attack Command. (campaign only)
Kick an enemy by vaulting over a cover. (campaign only)
Hit 10 enemies with your melee attack. (campaign only)
Buck the chain of command.
Play it smart.
Recover 12 Intel Items.
Face the horrors of war.
Kill 4 enemies with a shotgun in 10 seconds or less. (campaign only)
Engineer an exit strategy.
Kill an enemy just as they are throwing a grenade. (campaign only)
We have contact.
Kill 5 enemies using blind fire. (campaign only)
Look out below.
Sprint into cover 10 times while under fire. (campaign only)
What's lost is found.
Recover one Intel Item.