I just completed Mother Russia Bleeds. For that, I received the "sad ending" reward. I noticed that there is also a "happy ending" achievement, so there must be an alternative ending. Does anyone know how to achieve this alternative ending?
You have to beat the final boss without using drugs. Source
You can to solve it in a fight against the final boss of the game. You will get a good ending if you destroy him without drugs. It is important to understand that you do not need any treatment, don’t use - keys F and R. If you use medication or rage at least once, you will get absolutely bad ending.