Originally posted by H3y1tsChr15:

I understand to get the good ending i have to have positive moral, but i dont get it, i collected all the diary's, saved pavel, lestnitsky, and the bear, gave bullets to the homeless, didnt kill any monsters the dark one told me were not harmful, i even went non-lethal as much as i could (there were some exceptions such as the train, final mission and maybe a couple of other areas) but i still got the bad ending, im not going to replay this whole game, a lot of the stealth areas made me want to throw a chair at my monitor, but is there something i screwed up on? i thought saving lestnitsky, pavel, the bear, and surrendering enemies wouldve have guaranteed the good ending

If you play instruments, you will get extra morale points.
If you stop to listen to the dialogues of the NPCs, both those of the enemies and the allies and the people at the stations, you will also get many morale points. If you don't do this, the good ending will be very complicated for you. This has happened to many people and it is because they are in a hurry to move forward and rushing is not good. There is always time to relax.
When you're on the surface, explore as much as you can. There are hidden corpses, ammo caches, events, and hidden areas where there may also be ammo. And speaking of hidden areas, did you know that you can find secondary routes to avoid enemies? Well if you do that, you will get morale points.
Explore everything around you, but don't stay too long because otherwise you'll use up all the filters at once.
Did you kill the soldiers who surrendered? Under no circumstances do you do that.
If there are packs of monsters escaping or going somewhere in particular, DO NOT attack them. Hide and when they have passed you will gain morale.
At the stations he drinks a glass of vodka. It's not bad.
Take off your mask when Lesnitsky tells you to.

With these things, you will have a good chance of getting the good ending.

From what I understand, Metro here has a percentage system, so you might get lets say 80% good ending, but it fallen on bad ending.

bad

It may be a bit late but: The ending depends on the Moral Points, you get them when the screen flashes brightly with a specific water sound. Additionally, you can lose them as well. In order to get a good ending, you have to reach the ending with at least 110 moral points. You can check the Metro Wikipedia page, section Moral Points, there is a list of each point that you can earn/lose in every level.
Overall, you can kill enemies and still get a good ending, as far as I know, you can get some points on some levels if you complete them in a non-lethal way, however, there is no penalty for killing armed enemies.

https://metrovideogame.fandom.com/wiki/Moral_Points