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