**METRO LAST LIGHT**
In the level BANDITS you'll come to a point where you kill some bad guys and untie a soldier. He is gonna move a car forward on the tracks so you can pass with your car (Regina).
Just keep going forward, without Regina. You will come to an open room/area to your right. It will be a bathroom/restroom area (there is a diary page here). Take out the light (and any lights you come to for the rest of this guide) and hug the wall near the entrance. After a few seconds there will be someone who walks by and stops, this is your first knife throw.
Now go to the opposite side and continue moving forward. You will come to some stairs and a train car will be to the left. Now just start at one end and move your way through the train to the other end, throwing knifes at all the sleeping soldiers, one by one. There will be a couple of guys who are awake but as long as your crouched, vigilant, and turning off the lights as you go, you will not have an issue. At the end of the train, there will be two guys awake. Throw a knife at the closest one to you, then another at the next guy.
If it still hasn't popped, go back to the end of the train we started at, and on the complete opposite side will be another area/ corridor where you can basically do the same thing.
ATR NAD pointed out that reloading a checkpoint DOES NOT reset the counter.
Just move slow and turn off any lights. I promise this is super easy. If you have questions, I will help as best as I can.