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