In 'For a Lost Soldier' novel, perhaps there is a young boy or girl who forms a connection with the soldier. This character could bring out different sides of the soldier's personality. And of course, there may be other soldiers or military personnel who play important roles in the story, either as comrades or antagonists to the main soldier character.
I think loss is a significant theme in this novel. Characters lose their innocence, their normal lives due to the war situation. And perhaps there is a theme of self - discovery as well. As the story progresses, the characters might discover new aspects of their personalities while dealing with the challenges presented in the plot.
In 'the winter soldier novel', the most prominent character is the Winter Soldier. However, other important characters may include those who are trying to help him break free from Hydra's control. There could be some fellow soldiers or agents who discover his true nature and decide to assist him. Also, antagonists within Hydra who will do anything to keep him under their control are likely to be part of the main characters in the story.
There is Captain Edward Ashburnham, who is the 'good soldier' of the title. He appears to be a proper and noble military man on the surface.
In the 'Soldier 76 Graphic Novel', Soldier 76 is surely a main character. Additionally, there may be characters who are important to his backstory, like his superiors or subordinates from his military career. And perhaps some new characters created specifically for this graphic novel to drive the plot forward, either by helping or hindering Soldier 76 in his journey.
I'm not sure specifically as I haven't read it. But it might have a protagonist who is the soldier king. There could also be his comrades, his commanders, and perhaps some antagonists like enemy soldiers or traitors within his own ranks.
Since I haven't read the book, I can't say for sure. But they could be the lost boys and girls themselves, with each having their own distinct personalities and backstories.
Perhaps there are also some supporting characters like a wise old woman who gives the lost girls advice. Or a young boy who befriends them and helps them in some way. There could also be an antagonist, maybe someone who is trying to keep the girls lost or is causing the problems they are facing.
The main character in 'the lost weekend novel' is an individual who is deeply entrenched in the grips of alcoholism. He is at the center of the story, and his experiences, his highs and lows related to his drinking habit form the core of the narrative. There are likely other characters such as those in his social circle, perhaps a friend who tries to help him or a family member who is worried about his condition. However, to get a more comprehensive understanding of all the main characters, one would need to thoroughly read the novel as their roles and significance may be more nuanced and complex than what can be initially assumed.
Since I'm not familiar with the 'lost stars novel', the main characters could be individuals with different backgrounds and personalities. Maybe there's a misfit who doesn't fit into the norms of society, and a more conventional character who helps the misfit on their journey. There could also be a mentor - like figure who provides guidance to the other characters as they struggle with their 'lost' states.
I'm not sure without reading the novel specifically, but they are probably the lost girls themselves and maybe the people who are looking for them.