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