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