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