There are 91 possible points, but you need 50 of them for the good ending. Unlike Metro 2033 REDUX, you can kill humans (unless they're innocents/hostages) with no consequence unless a level on the guide says otherwise.

"Well why can't we use a REDUX guide"
That's simple: Redux and the original changes some of the rules and moral points around. So this guide is specifically made for the original.

If there aren't levels mentioned, that means there aren't any points to gain/lose.

You cannot tell if you got the minimum requirement, unless you reach the ending. It is dumb, but it is what it is.

Gain:

• After coming up the stairs, talk to the guard that tells you another patrol was attacked after he sits down. ("Many want to leave the station..."). (+1)
  
• Talk to the people in line before the hospital ("Doctor hasn't said anything"). (+1)
  
• Talk to the girl sitting on the ground next to the people in line. She will first say "We just have to hope." Then give her a few seconds and talk to her again and she will say: ("Leave me alone.") Walk away as she asks and you will get a moral point. (+1)
  
• Talk to the guard that opens the door to the hospital after he sits down ("People want to see their relatives."). (+1)
  
• Walk under the light on the right in the first room of the hospital. There is a torn fabric curtain on the right-hand side which you can walk through, leading to another torn fabric right in front of you. Walk through both these curtains to find sick NPC characters and obtain the moral point. (+2)
  
• Take the postcard from Hunter. If Artyom is not standing close enough to Hunter to take the postcard, he will leave the postcard at his left side. Pick it up to gain the moral point. (+2 if taken from hunter, +1 if picked up from the ground)

Gain:

• Play the guitar in Artyom's room. (+1)
  
• Play the balalaika (triangle guitar) near the father and the child drawing on the floor. (+1)
  
• Approach the man and woman sitting in the general market area with a teddy bear between them. As soon as the woman stops talking, you will be able to talk to the man. He will tell you about his sick child and asks you for a few bullets. Give them to him. You will lose about 2 MGRs. (+4)
  
• Open the door to Alex's room, prompting his dialogue. (+2)
  
• Exhaust all of Alex's dialogue options. (+1)

Lose:

• Take the MGR from the hat next to the man playing the guitar. (-1)
  
• There are two men sitting on a table just right from the table with the drunk man who is being scolded by his wife. If you talk to them, they'll start talking about some business. If you talk to them again, it will count as interrupting their business and you will lose a moral point. Because you cannot actively engage in conversations in Metro 2033, it's best you avoid that area or you might lose a point accidentally. There is nothing interesting there anyway. (-1)

Gain:

• Give a bullet to one of the beggars located all over the place. It is only effective once. (+1)
  
• Give a bullet to the kid to guide you to Bourbon. Note: Even if you have no MGR left but still enter the command to give him bullets, you will receive a moral point and the child will reluctantly guide you to Bourbon. Also, if you first refuse to give the boy a bullet, you will still be able to find him after he has run off and get the point. This is useful if you want to get the achievement Realist as well as the moral point. (+1)

Lose:

• Find Bourbon without the kid. This only triggers once you find him, not if you initially refuse the kid. (-2)
  
• Disturbing the man sleeping located near the kid that guides you to Bourbon if you do not give him the bullet. (-1)

Gain:

• When Bourbon talks about strange sounds and pipes, crouch next to the pipe on the right side of the tunnel until you hear laughter. (+1)
  
• After listening to the pipes, go left into the room where the dead body where the Tihar lies. Going back and listening again to the pipes for some more seconds will hurt you (this does not happen in Redux) and give you a moral point (same procedure as in "Khan"). (+2)

Gain:

• Get into the first train car you encounter by jumping on the box on the left side. Inside there will be a box you can open with some dolls. Use one of the dolls to make noise and you will get a moral point. (+1)
  
• After a fight with some mutants, Bourbon will spot a Hansa railcar, informing you that they are looking for the bandits, and instructs you to hide. Crouch next to him and wait for the railcar to pass without being noticed for the point. (+1)

Lose:

• Get noticed by the Hansa railcar. (-1)
  
• Destroy the Hansa railcar (probably means killing the Hansa soldiers). This is assumed from the trigger karma_l06_destroyed_drezina. (-5)

Gain:

• Use the hookah in the bar. (+1)
  
• Give a bullet to the beggar who tells the story to the kid in the market area after the kid leaves. (+1)

Gain:

• In the first area, go up the stairs on the left. Follow the watcher that runs away and look out of the window it escaped through. (+1)
  
• After you and Bourbon become separated while entering the building. On the top floor jump down into the elevator to find a secret cache with a Tikhar. (+1)
  
• During the vision of a playground when outside, as long as you don't move (you can look around). (+2)
  
• Also during the same vision, if you take off your gas mask. (+1)
  
• After the above vision, you will eventually enter a building and go down some stairs. At the end turn right and go all the way to the end (where a grocery scale is) and you will find another secret cache. (+1)
  
• When you go out of the leftmost window of this building to proceed further, look left and down. There will be some wooden planks leading to a narrow ice path just above the water. Follow it to find a body. (+1)
  
• At the area where there is demon feasting on a corpse, enter the building leading to Dry and take a right through the trap-filled hallway to play the tape in the cache. (+1)

Lose:

• Run out or completely across, or open fire during the playground vision. (-4 for skipping the scene, -5 for shooting in the scene)
  
• Shoot the dark one sitting on the shed on the other side of the playground after the vision. (-3)
  
• Shooting the dark one looking at a dead stalker on the other side of a gate (where you find Bourbon in Dead City 2). (-3)

Gain:

• Using the hookah to smoke within the crate maze on the left yields a moral point. (+1)
  
• Do not kill anyone at this level (this will most likely conflict with the above as the hookah is right next to a bandit.) (+4)

Lose:

• Shooting Bourbon's dead body. Apparently this might be broken (-2)
  
• Shooting and/or stabbing dead bodies multiples times, triggers Khan's speech upon encounter: "You might also try to value life more fully. What humanity is there in killing the wounded?" (-2)

Gain:

• When Khan tells you about the singing pipes, crouch near the pipes and wait until you hear laughter, then move away. If you stay near the pipes for too long you will get hurt, but seem to gain 2 moral points. (+1 for hearing the "tube voice", +2 for hearing the "tube scream")
  
• When you reach the ghosts of the defenders, stay close behind Khan as you move through. On the other side, keep following him until he mentions he was with them when they died and only he survived. (+1)
  
• After you leave the tunnels, Khan will curse while in one of the rooms. In this room, there is a body hidden behind some barrels (look for the blood marks on the floor to find it easily) (+1)
  
• Two points are awarded for seeing the second anomaly. This may be mutually exclusive with losing two points for shooting the second anomaly. (+2)

Lose:

• Opening fire on the ghosts (-2 for the "wall ghost", -1 for the "women ghost", -2 for the train ghost)

• Stop when Khan tells you to and don't move (you can look around) until he starts talking again. (+2)
  
• After moving a bit forward, you will hear a nosalis growl, then see the anomaly moving fast toward it in the adjacent tunnel. As soon as you hear the growl, stop and don't move until Khan starts talking. (+2)
  
• After you jump into the area where you will fight nosalis, go to the right to the dead-end area where the nosalis will be coming from, check the dead body behind the box beside the right wall. (+1)
  
• After the fight with the nosalis, Khan will enter a train car. Straight out from the back of this car is a dead end with glowing mushrooms and stalagmites. There is a partial skeleton on the ground there that will award a moral point when approached. (+1)

Lose:

• Shoot the first anomaly. (-2)
  
• Move when the second anomaly appears. (-2)
  
• Shoot the second anomaly. (-2)

Gain:

• You get a point for showing up, and listening to Khan when he explains the situation. (+1)

Lose:

• Run away before Khan finishes talking. (-1)
  
• Any type of hostile action in the shrine (e.g. Even slashing the knife). (-2)

Gain:

• Sneak up to the back of the train you fell out of upon the start of the level and finish listening to the officer's speech. After you get the point start backing away or they will spot you. It is recommended to put out the lamp leading up to the train on the left. (+1)
  
• In the dead-end tunnel through which the player arrives at the start of the level, kill or avoid the patrolling soldiers. On the right side of the tunnel, almost at the end, there is a small red wall box - pick up the MGR inside for a moral point. (+1)
  
• Just left from the train car, go down the stairs and listen to two guards talking about the secret entrance to the enemy base. (+1)
  
• Witness the execution of a Communist "deserter" without interfering.(+1)
  
• Go to the opposite direction of the deserter execution area until you find a flight of stairs. Go up the stairs a bit to listen to a soldiers conversation about suicide bombers. (+1)
  
• In the bottom of the front line (below the bridge), where Artyom must use the gas mask, there will be a pile of wreckage with a buried body's protruding arm holding some MGR. Take the rounds for a moral point. The arm holding the bullets is in the centre of the pile. The pile is at the bottom of the shaft of light shining through a gap in the bridge. (+1)
  
• In the Nazi part of the level, downstairs there is a room containing a couple of guards and a Helsing spear gun. In one of the corners (near the manhole), there is a small red locker. Open it and collect the contained ammo to get a moral point. You will see a drawing inside. The sound of the door creaking also alerts the guards, making it practically impossible to get this point if you want to do the level completely stealthy. (+1)
  
• The last moral point is awarded for freeing the three captured Communists in the Nazi part of the map, in the area after the rail car. To free them you need to kill all the Nazis here except the one at the very end of the tunnel. You will know it's done when their leader will stand up (The Nazi soldier will execute the leader if you wait too long when you get there). Talk to him. Killing the Nazis will prevent you from getting the stealth achievement for this level. (+1)
  
• Alternative: Complete the level without getting in a fight and you achieve a moral point (and the stealth achievement). The other side of the medal is that you can´t free the imprisoned Red Army soldiers and leave out the metal locker. In the Redux version, this point can be obtained if enemies are knocked out instead of being killed. (+1)

Lose:

• Kill any wounded men lying near the staircase (behind the bridge post). (-1)
  
• Kill one or more of the captured Communists. (-1)
  
• Kill everyone (this happens even if all enemies are only knocked out but the deserter, wounded and captured are killed). (-3)

Gain:

• Pick up the message tape the captain gives you after the fight. (+3)
  
• As you come into the station, go straight and into the railcar. Walk through all of it and exit on the other side for a flash point (Look out for the tripwire inside). (+1)
  
• Inside the first area of the station, go up the stairs into what looks like a hospital. Go in deep enough.(+1)
  
• As you're leaving the first area of the station and crossing over to the area where you need to use the gas mask, look left. There will be stairs blocked by a grating. Go through the door on the right and there will be another set of stairs with grating, but here the door will be open. Go up and then left over a makeshift bridge to find a lot of goodies. (+1)
  
• In the previous moral point area, you can hear music being played below you. To reach it, backtrack into the hallway where you need the gas mask and go left until you reach another railcar sitting at a station. To your right is a metro tunnel with a red light. Go left towards the dead end, where there is a dead body, some ammo and tape recorder playing music. You get a moral point when you get close. (+1)

Lose:

• Walk away from the wounded commander without taking the tape. (-1)

Gain:

• Refuse to take the reward from Sasha's mother at the very end of the level. (+5)

Gain:

• After climbing out of the building you start in at the beginning of the level, on the surface, you will eventually reach a house full of Nazis. Climb all the way to the roof and play the tape you got from the captain in the Defense level. (+5)

Gain:

• Completing this level without any enemy casualties will yield a moral point. You get this point when you meet up with Ulman at the end. (+1)
  
• Take the weapon given to you from Ulman in the beginning. (+1)
  
• Listen to the two Nazis talk about moving to Hansa until they are done. (+2)
  
• In the next area, kill or sneak past the patrolling Nazi and go right. There will be two Nazis near the end of the hall. You will have to use a throwing knife or silenced weapon to take out the light in the hall or else they will see you. If you wait until they stop talking about morals, you will get a moral point. (+1)
  
• Sitting nearby when the Nazi commander commands two other guards to watch the generator (+2)
  
• Turning off the generator. (+3)
  
• Destroy the generator. (+2)
  
• There is a room under the main area where the Nazis are in mass. This room has boxes which must be scaled. Once scaled, you will get yourself a morality point and if you look at Charles Darwin's book you get another. (+2)
  
• Listening to two Nazis talk about 'Metro 2' near the end of the level. (+2)
  
• Being nearby at the end of the level when the drunk Nazi is muttering to himself. (+1)
  
• After dropping into the tunnel where you need to wear a gas mask on the way to Ulman, keep an eye out for a bloodstain on the floor that leads to a corpse on your left. (+1)
  
• After meeting with Ulman and riding the metro cart for a while there will be a cutscene with a dark one, after the wall breaks and you are told to run, instead, walk towards the dark one for a moral point. (+5)

Lose:

• Fire a weapon while Ulman is talking to you at the very beginning of the level (right after he killed the guard). (-1)
  
• Run away from the Dark one during the dream sequence at the end of the level. (-3)

Gain:

• Before talking to Miller and saying you are "ready", look behind you and you will see Khan. Talk fully to Khan and you will get a moral point. (+2)

Gain:

• In the vision, approach the dark one when given a choice. (+5)

Lose:

• In the vision, do not approach the dark one. Instead, go the opposite way. (-5)

Gain:

• Do not take Boris' ammo or weapon after his death (-1)

Despite you getting all the moral points, you can still get the ranger ending. If you choose to not destroy the beacon, you will get the ranger ending. YOU HAVE TO destroy the beacon to get the Enlightened ending.

If you have more information or things that I could improve on this guide let me know!

I made this guide specifically for my achievement guide, you can find it here:
https://test-steamproxy.haloskins.io/sharedfiles/filedetails/?id=3374820923