Hatred is one of the purer emotions and it can distill into a poison.
Yet the words “I hate” are oddly bereft of a stinger. It is almost a childish way to begin a sentence – like a five-year-old mutinously surveying his dinner plate and muttering, “I HATE broccoli.” The underlying emotion just isn’t there – it’s been enervated, down to a basic repudiation and nothing more.
But hate can go deeper. SO much deeper.
You can ‘hate’ broccoli, or anchovies, or cilantro, the smell of tar, the color purple, or that fish. What you mean is that you want to steam past those things and you don’t want anything to do with them. But you don’t give it much thought. You ‘hate’ them when they’re in front of you, when your senses are stimulated by them.
Then there are things that you hate consistently because they offend something in you — stupidity in the form of willful ignorance. Bigotry. Prejudice. Arrogance, Selfishness… Fill in the blanks with whatever it is that makes your hackles rise. Other human beings hate other things — that another human is a different color, a different faith, identifies with a different gender. In other words, the hatred of the OTHER, classifying that other as so different from one’s self that it becomes ‘inhuman’ and therefore it becomes easier to think about destroying it.
There are ideas that you hate. Most of us hate the idea of war. Most of us hate the idea that a child suffers hunger, or cold, or abuse, although some will look at the children of a different race, a hated race, and either ignore the suffering or gloat over it.

What does this have to do with writing?

We have all said “I hate…”, we all know what it means. But when it comes to writing it? Oh, there are SO many nuances.
You can loathe something, or someone. You can despise them. You can dislike them. You can be averse to a taste, a temperature, or an idea. You can abhor something. You can be uncomfortable in the presence of something which makes you ‘hate’ it. You can be bored by it. you can recoil from it, you can spend your life avoiding something, or you can hate it so much that you can dedicate your life to making it disappear.
Hate can be a weapon, a powerful weapon, for both good and evil
It is a major reason for war, or at least a way to sell it to those who have to fight it. But someone who hated the idea of polio, or dolphins dying because of oil and plastic pollution, or trophy hunting, or human trafficking, and who focuses on doing things that make those bad things better… could do a WORLD of good.
What do your characters hate? What do they dislike? What do they loathe? What do they find unpleasant but can live with – the lowest level of ‘hate’? What do they despise, detest, find objectionable? How much of their energy and their mental focus are they willing to spend on hating that thing? Do they just hate it or are they willing or able to do something about it, to make the thing they hate disappear, or to improve it, or to change it in a way that they might find it easier to like? Does this involve changing themselves?
What your character hates can be a hugely important building block in making that character live, breathe, step out of the pages of your story and shake your reader profoundly.

They’ve got to hate SOMETHING.

They’re human (yes, even if they’re elves or aliens, they are human in storytelling. You wrote them, You created them. YOU are human. your readers are human. It is the humanity in these other creatures that they will be looking for. Give your charcters a hill they hate, a hill beyond which they will not go. Give them a small dislike, give them an aversion, give them a incandescent hatred of someone or something which will shape the days of their existence.
Look in the shadows of their mind. There are things there to hate. Always. Bring them into the light. Make those things important.
Even if it is just the smell of tar.