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 TOWER level.
Spend 1 hour on the DEVELOPER 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.
Disarm 10 Traps.
Destroy D6.
Kill Pavel.
Complete the game in Survival Mode.
Complete the BRIDGE level without a kill.
Kill all armed enemies on the REVOLUTION level, including all reinforcements.
Kill 10 enemies in a row with Throwing Knives.
Stealthily kill 15 Enemies.
Save D6.
Complete the game in Spartan Mode.
Complete all 43 of Artyom's hidden Diary pages.
Kill 100 Human Enemies.
Make Moskvin tell the truth with help from the Dark One.
Save the Bear from the Watchmen after the fight.
See all Visions in the Dead City.
Find out about the Reds' plans.
Remove your mask when Lesnitsky demands it.
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.
Spend 30 minutes' worth of Filters.
Kill the Watchmen attacking the Railcar without taking any damage.
Open 10 locked safe boxes.
Complete the REVOLUTION level without killing and raising an alarm.
Turn off 40 Lights without breaking them.
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.
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.
Free the Prisoners.
Finish the ASHES level without taking a hit.
Complete training sequence.
Choose three primary weapons that use different ammo.