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