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