on Writers Helping Writers:

No one in the real world is perfect, and so characters shouldn’t be either. To seem as real as you or me, they should have flaws and strengths, and these sides of their personality should line up with who they are, how they were raised, and reflect the experiences they’ve had to date, good and bad.

While we develop our characters, however, we need to remember that flaws come with a tipping point. If we write someone with an overabundance of negative traits and behaviors that are a turnoff, the character will slide into unlikable territory. And yes, if the goal is to make a villain, antagonist, or other character loathsome, that’s fine–mission accomplished. But if we want readers to be on their side, too much surliness, negativity, secretiveness, or propensity for overblown reactions can cause a reader to disconnect.

Like a joke taken too far, it’s hard to claw an audience back once they’ve formed negative judgments, which is why we want to be careful and deliberate when showing our character’s negative side. Antiheroes tend to wear flaws more openly and can be semi-antagonistic as they battle the world’s constraints, so this line of likability is something to pay close attention to if we want readers to ultimately side with them.

Here are some tips to help you.