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.
Live and let die.
Complete game on "Suicide Mission" difficulty.
Complete game on "Combat Op" difficulty.
Choose restraint.
Buck the chain of command.
Kill 150 enemies with any heavy weapon. (campaign only)
Kill 10 enemies while they use zip lines or are rappelling. (campaign only)
Kill 50 enemies with any sniper rifle. (campaign only)
Kill 50 enemies with grenades. (campaign only)
Kill 75 enemies with any shotgun. (campaign only)
Sprint into cover 10 times while under fire. (campaign only)
Kill 4 enemies with a shotgun in 10 seconds or less. (campaign only)
Live and let live.
Carry on, soldier.
Complete game on "Walk on the Beach" difficulty.
You are relieved.
The end of the line.
Kill 250 enemies with headshots. (campaign only)
Choose vengeance.
Get out of here!
Blow up 10 explosive objects, killing at least one enemy each time. (campaign only)
Kill 350 enemies with any rifle. (campaign only)
Hit 10 enemies with your melee attack. (campaign only)
Stand united.
Kill 5 enemies using blind fire. (campaign only)
Kick an enemy by vaulting over a cover. (campaign only)
Show mercy.
Stun an enemy by dumping sand on their head. (campaign only)
Follow your orders.
Kill 3 enemies with a single grenade. (campaign only)
Play it loose.
Kill an enemy just as they are throwing a grenade. (campaign only)
Kill an enemy by tagging him with a sticky grenade. (campaign only)
Kill 100 enemies with any pistol or SMG. (campaign only)
Face the horrors of war.
Kill an Edged Weapon Expert while he is up to 5 meters away. (campaign only)
Engineer an exit strategy.
Recover one Intel Item.
We have contact.
Look out below.
What's lost is found.
Play it smart.
Save a bullet.
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.
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)