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