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