Soldiers are very likely to be characters. They are the ones directly in the line of fire and experiencing the horrors of war first - hand.
In 'War is Hell Short Stories', it's probable to find characters like medics. They are the ones trying to save lives in the midst of chaos. Then there could be refugees, fleeing from the war - torn areas, their stories highlighting the displacement and desperation. And let's not forget the families of the soldiers, their worry, grief, and hope would add depth to the narrative.
Given the title, there are likely to be female characters, specifically girls. They could be soldiers, nurses, or civilians caught in the war. There may also be male characters who interact with the girls, such as fellow soldiers, commanders, or family members.
There could be gardeners or nature lovers as characters. They might be the ones observing or taking care of the forest of flowers.
Definitely Harry, Ron, and Hermione. They were the central characters during the war and would likely continue to be important in the post - war stories. They would be using their skills and experiences to shape the new wizarding world.
Obviously, Katherine herself. Also, there could be appearances from demons or other hellish creatures that are part of the hell setting. Given her history, Stefan or Damon might make appearances in her memories or even in some sort of spectral form if the fanfiction has elements of the afterlife being connected to the living world.
The main themes are likely to include the brutality of war. It might show how soldiers and civilians endure great pain, suffering, and loss. Also, themes of heroism in the face of extreme danger could be present.
Most likely, Sam and Dean Winchester would be main characters. They are the central figures in the Supernatural series, and any fanfiction set in that universe would probably revolve around them. They are the ones who usually deal with the chaos and the supernatural threats.
Journalists who have reported from war zones could be narrators. They've witnessed and documented the events, so they can provide a unique perspective. Also, civilians who lived through the war and have a story to tell might be narrators too.
Tris and Four would likely still be main characters. Their relationship has been a central part of the Divergent series, and in a post - war scenario, they would be key in leading the rebuilding efforts or in bringing about change.
Obviously, Sasuke and Sakura are likely to be the main characters, given the name 'sasuaaku'. They are two very important characters in the Naruto universe, and a post - war story about them would be quite interesting.
Zuko is very likely to appear. As her brother, he would play a crucial role in her life after the war. He could be the one trying to help her redeem herself or dealing with her if she still poses a threat. Mai and Ty Lee could also be there. They were once her friends/companions, and their relationships would be interesting to explore post - war. Maybe they would be hesitant to trust her again at first. Aang would be another possible character. As the Avatar, he might be involved in Azula's fate, whether it's in terms of forgiveness or making sure she doesn't cause more harm.