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