allow your characters to be fuckups. total assholes, even. flawed characters with redeeming qualities are more interesting and likeable than characters who are one-note good (like charlie and michael in lost). First off, I'm going to stop using the word 'likeable', because it has two separate, conflicting meanings. characters being likeable (morally agreeable, someone I could hang out with) is separate from them being likeable as in interesting to read about and understand (endearing). Give your characters actual flaws, not job interview flaws. Here are a list of fake flaws:

• Being clumsy or awkward (??)
• Being late or forgetful
• Being too much of a good thing (honest, kind, hardworking)
• Being stubborn
• Having a quick temper or sharp mouth

Fake flaws either fall into the category of minor personal traits incorrectly called flaws or double edged swords that only ever seem to work in their favor. Minor personal traits could stay, but they're not flaws because a) nobody will reasonably take an issue with them over that and b) they will never negatively affect them, and when they do, it's more accidental than their fault. Double-edged swords are perfectly fine to keep in when done correctly, however most of the time they don't actually swing both ways. For example, a character that is very stubborn because they KNOW they're always right, and never put themself in a bad situation from being stubborn over something stupid. Quick-temper type characters are especially annoying, because not only are they rarely hurt by it, they just aren't as fucking funny as the author thinks. I will literally root for this character's death. Basically, the author is just telling the reader that something is a flaw without actually showing it being a flaw , and the end result is a character (or author) who's incredibly obnoxious and self-righteous.

MORAL DISAGREEABILITY /= BAD CHARACTER

A lot of writers might be afraid of a character not being morally agreeable, but that's not the end of the world. Every reader brings their own baggage into a story and no one character is universally loved. Your reader won't hate your MC for having a real flaw or dislikeable trait, if they don't have flaws, your readers will be fucking BORED. If they don't have flaws, they don't read as human.

Realistic, hard-to-contort flaws are not one-off traits, but stem from a flawed worldview. Here are some examples:

• hypocrisy (i like all my characters to be a hypocrite in at least one way)
• being possessive or controlling
• being elitist or condescending
• being socially inept (not in a cute way, like having no sympathy, misinterpreting other's intentions, oversharing, saying things at the wrong time)
• being bad at communication over problems and avoidant of any confrontation
• having a victim complex
• being emotionally avoidant, cold, or hypervigilant
• being bigoted
• being an ideologue who derides other's points of view
• being double-faced or a liar
• narcissism, self importance or self righteousness (that is, when the author intends so as narrative truth)
• not being able to admit their own faults, much less learn from them
• being a perfectionist or not allowing themselves to make mistakes
• having destructive habits they are unwilling to change

Do flaws need to be fixed?

No. If someone has these worldviews, you will likely elaborate on why that is. I don't consider my own characters flawed for behaving in these ways, because these behaviors come from their personality and life experiences. It is rational for them to act in these ways as that's how they've coped and made sense of the world. These develop over the story, of course, but to have them throw their hands up and admit they are wrong would be to fundamentally change them as people, to neuter what makes them who they are. They are not going to realistically throw away a deep seated mindset because it's "wrong", especially not overnight. They can change and adjust, or experience cognitive dissonance. People don't radically change in character IRL, though, at least not without a sound progression. If the flaw is creating instability in themself or their surroundings, they will likely find some way around that. That doesn't necessarily mean admitting they are wrong.
Especially in fantasy and spec fic, why would characters need to change to our current value system? Maybe they see a new benefit in being nice to their friends or something. But for example, if you have a character who lies to get what they want frequently, and honesty would actively make their life worse, and there is no cultural value to honesty, why would they choose to do that?
Likewise, even if they start out their story a deeply flawed person, they shouldn't end the story as Buddha. Even if their arc involves addressing one of these flaws, they don't have only one flaw because no one does! Also, their arc doesn't necessarily have to involve them fixing these flaws. Realistically, even if they see a problem with one of their behaviors and wish to change, it can take years to do so. They also don't need to call out their flaws directly to the reader (nor do other characters). Please no therapy speech also. I understand those monologues are tempting because they show a moment of personal change, but they are contrived, and personal change rarely comes about that way. I'll do a post on character arcs at some point.