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