I'm thinking of this question in context of your other question. As you know from my answer there and my comments above, I am a sucker for identifying with a protagonist and a happy end for him. Nevertheless a story of a group of people who die off one by one, with one or a few survivors reaching the end of the tale, could be satisfying to me. To achieve that, you could try one or all of the following:
Readers will identify with whichever characters appear to be central to the narrative. Readers expect the "lives" of these central characters to be meaningful. If they just randomly die, that is like a slap in the face of the reader's trust. Nevertheless that is life. It is realistic that people die randomly. There is no divine plan to my grandmother's death. What makes it bearable is my perception that her live has been meaningful for her and that I remember her and learn something from her death. My grandmother's death is something that makes me grow as a person. It also makes me love and appreciate the other people in my life more: my son, my girl friend, and in fact everyone I meet or just pass by on the street. The death of my grandmother makes life valuable and meaningful.
So if you have a group of central characters, and your readers do not know which one of them will survive, what makes their deaths a "positive" experience for the readers is if the narrator or the other characters reflect on that "person"'s life, their achievements and failures, and if that reflection causes them to grow.
For example, a fighter could have an opponent whom he manages to kill. But instead of simply turning the narration to other matters, the fighter could have a moment (or many moments spread over the following narration) where he thinks about the opponent, how he had a life and a goal that were just as valid as his own, and what it means for his life and goals that he thinks he can just reach them by killing that person. And he might come to the point where his goals no longer appear valid to him. In that story, the opponent was not just an obstacle that looses all relevance once it is overcome, but a person. Similarly, the fighter is not just a plot device, but a person with feelings and emotions whom killing someone does not leave unaffected. Or if it does, then that is that person's growth and development.
If you have a number of characters, who all go through the same story in one way or another, they are probably in some kind of relationship with each other. They may be a team, a family, friends, enemies, people on the same bus, whatever, but their relationship through being part of the same events will make them care about each other. This care can be negative (glad he's gone) or positive (sad he's gone) or without direction (shocked at the death), but that does not matter for the death having an influence on them and changing them.
For example, if you have people on a bus, who don't know each other at the outset, and they are caught up in some plot and they start to die off, the people begin to care about each other. A common enemy may bring them together; an enemy hidden among them may cause them to turn upon each other. In any way, they will relate.
So if you have a tale of a group of people, and at the outset you want it to be not clear who is the final protagonist, and you want most of the people to die during the story, then begin the story without a protagonist. Give equal weight to all characters. And when they begin to die, start to have the deaths change the relationships among the people, and the people themselves. And slowly, over the course of the narrative, bring certain survivors more to the front of the narrative, show how their outset-personality and their changes helped or hindered them in their attempts to get through whatever is going on. And integrate the dying somehow into the surviving. Make what the dead did meaningful to those that survived.
