: What meta-properties should a character have in general? What are the properties a generic main character from a character-driven/psychological novel should have? E.g. relations, motives, personality,

Persistence.
That is the only personality trait that seems essential to a main character. They don't give up; at least not permanently. Their goals may change, they may face the inevitable and even die in the end (like in some cancer stories), but whatever they defined their problem to be; they don't give up. They solve it. Perhaps for a dying mother, her problem is, before she dies, she will reconcile with her daughter. The problem to solve is not that she is dying, it is to accomplish something before she dies.
Likewise, a story may end with the MC sacrificing themselves to accomplish something greater; but then they solved their problem.
An ending in which the MC just gives up is not satisfying (unless he has made a choice on what he wants; i.e. he has to give up A to get B or vice versa). So while we all DO give up on things in IRL, that is not good fiction.

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If this is your first attempt, then you actually you don't need anything special, just behavioural loops. Even one would suffice.

Your character will start as fully circling in one loop. As they try to break it, they fall in the next one (or back to the first one) with excruciating internal pain.

A simple example.

Bob likes cookies. He eats a lot of them. He then feels sick and swears he'll never do that again. Four hours later, when he is hungry, he'll look at the cookie jar and tells himself that a last one will not harm him.

You want to focus on the mental loop of self-denial, and self-gratification. Make Bob feel guilty when he gives up his promise, and make him feel righteous when he promises again. And when he tries to break free, wait a few pages and then make him go in a frenzy to the nearest store to gobble cookies on the way home.

As you can see, it is a simple and effective way to crack into your first character driven psychological story.

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properties [of] a generic main character of character-driven/psychological novel

Short Answer:
A very long list. Oh, and a degree in Psychology helps.

Long Answer:
Assume that you are an MC in such a novel. What makes you an individual and, therefore, will make the character a deep, fully fleshed one?

Let's ignore the physical appearance for now, and focus only on the psychology.

Look around for different personality tests. They all have something that makes sense, but they all tend (IMHO) to fall a bit short from reality. Study the different personalities and see all the factors that make them different. Make sure to work with at least two or three different personality (16 personalities, the big five, Jung, Briggs Meyers, the zodiac, anything!).

At this point you want to identify what could make different characters (with different personalities) react in different ways to the world. Then compare those personalities to yourself and to close friends/family. How well do those personalities match them? Why? What do you disagree about within the theoretical description in relation to the reality?

Once you've finished that analysis, focus once more on yourself. Think about what you value the most and what you dislike the most: honesty, friendship, etc. Look at different people around you: can you tell what they value and dislike from their actions alone? Can they do same for you? How do your values come through in your actions? Do you ever act in contrast with your values (eg. you value honesty but lie to your friends)? Why? How do you feel when you go against that value?

At this point, you are trying to understand why people act the way they do. Why do they sometimes go against their (alleged?) core values and how does that affect them?

Next, focus on fears. What do you fear the most? This can include phobias, I suppose, but it's mostly about deep existencial fears: fear of growing old, of being hurt, of being humilliated, of failing and being called out on it, etc. Try to see how your fears drive you into, and away from, new experiences.

These fears tend to dictate how one reacts to even the smallest event. If one is insecure and dreads having a mistake being pointed out in public, they'll react defensively to an innocent 'hm, interesting shirt'. They'll first and foremost imagine their fears being turned into reality and assume the person thinks you've made a mistake when you bought the shirt, when perhaps the person is thinking the unusual choice is surprisingly nice.

Look up a list of the 5 / 10 / 20 top existencial fears if you can't think of many. While you're at it, look up reasons behind conflict in relationships: conflict is caused (or avoided) and dealt with in very different ways and for a great number of reasons. Obviously, they vary depending on whether we're talking friends, family or lover/partner.

Conclusion

It's way too much research, one might say. Well, if one wants to have a deep psychological novel, one must understand what drives a person through life, so the character can then mimic it. Your question makes me think you've never thought very deeply about what makes a person act the way they do, so... yeah, lots of research.

Simple life experience is an alternative, true, but that usually requires a lot more years of hands-on practice than just a couple of weeks of theoretical research.

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If you view characters as a discrete set of properties, especially in a psychological novel/story, then frankly, you're not going to succeed. Can you summarise your mother as a discrete set of properties? Your father, your best friend, any siblings you might have?

If you can, then you think in a very different way to most people.

The most effective way to build a character is to form a full person; they, like any real person, were formed by their childhood experiences, their parents, even their genetics to some extent. They may have hope and dreams, or they could be a defeated cynic. They might be good at life, they might be loser.

But what's important is that you write them as a person, not a stat list. Perhaps DeviantArt will accept character creation done in this manner, but if you intend to write a psychological novel, try giving your characters a psyche worth analysing.

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