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 KSHATRIYA level.
Complete the PAVEL level.
Complete the KHAN level.
Complete the ANNA level.
Complete the SPIDER LAIR level.
Complete the SNIPER TEAM level.
Complete the HEAVY SQUAD level.
Save the Bear from the Watchmen after the fight.
Complete all 43 of Artyom's hidden Diary pages.
See all Visions in the Dead City.
Open 10 locked safe boxes.
Complete the BRIDGE level without a kill.
Save D6.
Complete the game in Survival Mode.
Complete the REVOLUTION level without killing and raising an alarm.
Watch the entire Theater Show.
Complete the FACILITY level without killing or raising alarm.
Complete the SEPARATION level without killing or raising alarm.
Kill 10 enemies in a row with Throwing Knives.
Destroy D6.
Complete the game in Spartan Mode.
Make Moskvin tell the truth with help from the Dark One.
Kill Pavel.
Find out about the Reds' plans.
Remove your mask when Lesnitsky demands it.
Kill the Rhino.
Kill 100 Mutants.
Turn off 40 Lights without breaking them.
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.
Spend 30 minutes' worth of Filters.
Kill the Watchmen attacking the Railcar without taking any damage.
Kill all armed enemies on the REVOLUTION level, including all reinforcements.
Kill 100 Human Enemies.
Escape from the Red Line.
Complete the ECHOES level undetected by the Watchmen.
Burn 50 Cobwebs.
Use 10 Lever Switches.
Make 10 Spiders flip belly-up.
Disarm 10 Traps.
Stealthily kill 15 Enemies.
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.