Here is the full list of all 49 Metro: Last Light Redux achievements. It takes around 30-35 hours to unlock all of the achievements on Windows.
Complete the KSHATRIYA level.
Complete the KHAN level.
Remove your mask when Lesnitsky demands it.
Spend 1 hour on the DEVELOPER level.
Complete the SPIDER LAIR level.
Complete the PAVEL level.
Complete the ANNA level.
Complete the TOWER level.
Complete the SNIPER TEAM level.
Complete the HEAVY SQUAD level.
Save D6.
Complete the game in Survival Mode.
Complete all 43 of Artyom's hidden Diary pages.
Kill Pavel.
See all Visions in the Dead City.
Complete the BRIDGE level without a kill.
Disarm 10 Traps.
Find and return the crying child's Teddy Bear.
Drink at every occasion.
Rescue the Women and Children on the BANDITS level without raising alarm.
Kill the Watchmen attacking the Railcar without taking any damage.
Make 10 Spiders flip belly-up.
Complete the REVOLUTION level without killing and raising an alarm.
Kill all armed enemies on the REVOLUTION level, including all reinforcements.
Open 10 locked safe boxes.
Watch the entire Theater Show.
Complete the FACILITY level without killing or raising alarm.
Complete the SEPARATION level without killing or raising alarm.
Kill 10 enemies in a row with Throwing Knives.
Destroy D6.
Complete the game in Spartan Mode.
Make Moskvin tell the truth with help from the Dark One.
Save the Bear from the Watchmen after the fight.
Find out about the Reds' plans.
Kill the Rhino.
Kill 100 Mutants.
Spend 30 minutes' worth of Filters.
Turn off 40 Lights without breaking them.
Use 10 Lever Switches.
Escape from the Red Line.
Complete the ECHOES level undetected by the Watchmen.
Burn 50 Cobwebs.
Kill 100 Human Enemies.
Stealthily kill 15 Enemies.
Escape the chasing Nazis on the REICH level without being caught once.
Free the Prisoners.
Finish the ASHES level without taking a hit.
Complete training sequence.
Choose three primary weapons that use different ammo.