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