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