Accomplish the indicated achievement to get the corresponding number of Gamerscore points:

Metro Trader (20 points): Make 10 deals in weapon shops.
Wheeler-Dealer (25 points): Exchange 500 Military Grade 5.45 rounds at Exchange kiosks.
Nosalis hunter (30 points): Kill 30 nosalises.
Fire in the hole (25 points): Kill 20 lurkers.
Heavy Reader (20 points): Kill a librarian.
Ka-Boom! (30 points): Explode 10 enemies.
Ranger (30 points): Find all Ranger stashes in Dead City 1 and 2
Old school (30 points): Kill 30 enemies with the double-barreled shotgun.
Exorcist (20 points): Complete levels "Ghosts" and "Anomaly" without dying.
Demolitionist (30 points): Blow up the tunnel and airlock at "Cursed" station.
Air gunner (30 points): Kill 30 enemies using pneumatic weapons.
Cowboy (30 points): Kill 30 enemies using revolvers.
Inquisitor (35 points): Kill 2 demons.
Rescue Ranger (30 points): Save a group of "Reds" from Fascist captivity.
Tank Buster (20 points): Destroy fascists' Panzer.
Raider (30 points): On the level "Depot" silently kill the first guard and break into the Fascist station unnoticed.
Ninja (30 points): Kill 10 enemies with throwing knives.
Slice & Dice (30 points): Kill 20 enemies with the knife.
Fugitive (30 points): Complete level "Armory" without getting caught.
DJ Artyom (30 points): On the level "Outpost" reach the radio tower and broadcast the commander's message.
Merciful (30 points): Complete the level "Black Station" without killing any Fascist Soldiers.
Pyro (20 points): Kill 5 enemies with a flamethrower.
Pathoanatomist (20 points): Kill 5 amoebas.
Quick Draw (30 points): On the level "Hunter" kill the nosalises before they break through the ventilation grilles.
Soft Touch (30 points): Disarm 10 wire traps.
Sniper (30 points): Make 25 headshots.
Heavy Metal (20 points): Kill 15 enemies using stationary machine gun.
Invisible man (40 points): Complete "Frontline" level without killing anyone.
Hedge-hopper (30 points): On the level "Frontline" kill all of the enemy Red Army and Fascist Soldiers.
Scrooge (30 points): Save 500 military grade rounds.

Additionally, there are nine secret achievements:

Metro dweller (20 points): A true metro citizen. You know everyone and have seen everything.
Explorer (30 points): There is no place in metro you did not visit
Generous (10 points): Help the poor, a coin for the kid, medicine for the sick. You help everyone you see.
Realist (10 points): A coin for a hungry kid? Get a job.
Sherlock (20 points): Found all gold ammo, hidden throughout the stations.
First blood (5 points): What doesn't kill you, makes you stronger.
Quick-witted (30 points): Break the support and activate the chandelier in less than 20 seconds.
Enlightened (20 points): Find the truth.
If it's hostile, you kill it. (20 points): Become a true ranger.