Our society is one of constant contradictions about what "good" even is, and doing the wrong thing, or even trying to do the right thing can just as easily be punished as it is rewarded, especially if the good thing actively goes against what the society wants (conformity, subjugation in the name of "law and order", everyone only exists to empower the machine/wealthiest, etc.).

But then you have Evil/"Morally Grey" stuff being portrayed and romanticized as "complex" and "cool"...

when in real life, evil is just boring in the way it's handled. The evil people in real life aren't criminal masterminds with cool and sexy stuff, but boring elderly assholes with too much power and being giant conformist hypocritical control freaks, surrounded by sycophantic easily bribed yes-men who are also just as dull and stupid as they are.

All of this, right here. All of it.

Good isn't easy. It isn't straightforward. It can be two contradictory things at the same time. If it was easy, everyone would do it, the reason that so many people are evil is because good is hard.

Evil is just being selfish and small and lazy.

‘Realistic’ can be a pretty subjective word in writing, but I just wanted to say:

Something I want to see more of is blurring the lines in character’s morality. I do know that this isn’t universally applicable--given that some characters are intentionally 2-dimensional for plot reasons--but it can facilitate crafting of the much debated anti-hero, anti villain, and morally grey archetypes.

Recently I have been reading an incredible comic called ‘V for Vendetta’, which I believe masterfully executed the complexities of humankind. In the book, V, an anti-hero who commits several acts of violence in the first 20 pages, is permitted a sense of humor and soft spot for Evey. What is so special about this is that the authors manage to use these small quirks V has to further express the brutality of what V must do to achieve his goals. Although he is by definition (however correct his views are) a terrorist, this does not stop him from treating Evey with respect (gasp! an edgy character who doesn’t abuse his friends?? what a thought) and even reading her bedtime stories.

The same goes for the more virtuous breed of characters. Although I know not everyone likes coffee, there is a reason coffee and doughnuts are marketed together! Everyone loves the ‘cinnamon-roll’ character, but eventually their unwavering innocence and fluffy optimism can grow stale. This is where I think it is important for them to diverge ever so slightly. Let them finally snap under pressure or seek solace in other characters. 

The fluid transition from sweet to bitter (as per my food example) allows for the more complex notes of both the pastry and the drink to be shown. 

Hi! 

It’s hard to say whether that would seem cliche or not because the truth is that it does happen. People make mistakes in wars, and unfortunately, there are many circumstances which may lead to massacres or the deaths of innocent people. 

Some of this depends on what kind of person is your character. If she’s a tougher, battle-hardened person, she might be making much more brutal decisions. Your character might be used to making hard sacrifices to win a battle. If your character is a more naive, inexperienced, or simply softer/easygoing person, they might be completely unused to making hard decisions or the necessary steps it takes to win a war. 

Also, if she was just following orders (assuming she may be a soldier of some kind), the mistake isn’t necessarily hers, but rather her superior’s (or whoever made the decision that led to the massacre). If she’s just following orders, it’s not really her fault. She was just doing what any soldier would do - follow the orders of their commanding officer. Now, obviously some people would still feel extremely guilty even if they’re indirectly involved or weren’t the direct cause of the situation. A lot of people who deal with the grief and trauma of similar situations tend to think in “What if”- type statements. E.g. “What if I had done something differently? What if I had disobeyed my orders? I should have done this instead.” You also say “haunted” rather than “guilty”, so your character may just feel horrible that people died because that’s a tragic event. 

If you really wanted to change it up, here are a few ideas:

Write your character as the one who made the decision, rather than her just following orders

Perhaps the decision she made was actually a good one - e.g. went into a warzone to save a friend, rescued a child from a burning building - but it led to disastrous consequences. For example, her going to rescue someone left a group of people/her soldiers vulnerable

Your character actually chose to do something horrible, and didn’t regret it until years later (maybe she sold secrets to the other side, smuggled weapons, took part in war crimes)

Character went AWOL/deserted and abandoned people who needed her help

Character was trying to prove her worth (possibly to earn glory/fame/a medal) and disobeyed orders; Alternatively, she switched units without letting any of her colleagues/bosses know, and that messed up her team’s plan that she left behind

I think sometimes the cliche lies in that the characters feel guilty when they 1. did their best in a horrible situation, or 2. didn’t really do anything bad in the first place, but feel that a specific consequence is their fault nevertheless. Very rarely do we see characters who feel bad and actually did something quite horrible. Part of this might come from a fear that if a character has, say, murdered someone or left someone for dead, they will automatically be labelled as “bad” or “villainous”, but the world isn’t so black and white, and sometimes people must choose the better of two evils. 

E.g. A ship captain chooses to close off the lowest decks of the ship to prevent it from sinking/gaining more water. By doing so, the captain trapped some of his own crew members, resulting in their deaths. However, he did so to save the rest of his crew, and had he done nothing, everyone would have died. 

The decision is obviously a tough one, and by itself, it’s a horrible deed because it’s essentially murder. But in the situation, the captain was not only doing what he thought was best, but he did what he knew would save countless others’ lives by making sacrifices. Or maybe your character just did something that was awful and uncalled for. Maybe they killed someone in cold blood, abandoned a family in need, stole from someone who didn’t deserve it; it’s your characters past, so they’ve changed since then. War is also crazy and affects people in different (and often harsh) ways. Looking into real war stories and the experiences of veterans from all different wars may help give you an idea. 

If you really think your character’s backstory might be too cliche, I’d suggest forgoing any backstory that tries to preserve a sense of goodness in your character. Don’t be afraid to let your character be gritty, or make bad decisions or do bad things. 

But I also think you could make your current idea work as well. You can always put an interesting twist on it, and if your story takes place during or after a war, or in a world where war is common or other characters were affected by the war, then her backstory makes sense and you could delve into her experience vs. other characters’ experiences with the war.