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