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