One of the earliest and most difficult lessons I had to learn as a writer was that the idea of perfection is more fun in theory than it is in writing. Perfect situations, perfect worlds, and especially perfect people can be the death of a good story, because the things you remember about the world, what makes the people and the things around you interesting, are their flaws, because in the end those are the things that distinguish them from everyone else.
For example, a while back I ran into a very interesting fellow who even now I can still remember as if he were standing in front of me. He seemed like a kind man with an outgoing manner and a good sense of humor, but his appearance led me to wonder if he had rolled out of a rotting cardboard box a few minutes before. He wore a faded, pinstripe suit that otherwise looked well-cared for. He had what people would describe as salt and pepper colored hair, including the hair on his beard, and it stuck out in all manner of crazy directions. His skin was a pallid color and was riddled with patches of rough, enflamed scabs (likely caused by a skin condition), and he had a mouth full of brown, crooked teeth that I desperately tried not to stare at. And to top it all off, whenever he tilted his head to one side or the other, I saw a small mound of dandruff fall and land on his shoulders, like snow off a roof in Spring.
This might sound like an overly harsh description, but from a writer’s perspective I found this man quite fascinating because he was truly unique. Every trait I observed in him begged some sort of question about his history. While the real world is fixated on beautiful people (like famous actors and actresses, supermodels, etcetera), in books they often have a disturbingly bland visual feel to them unless the author goes out of their way to give them some distinguishing feature. I imagine this is because these kinds of idols are chosen because they possess or represent specific ideals of beauty. In real life, you can tell one idol from another (at least most of the time), just as you could tell any other two people apart, but in literature the descriptions of beautiful people tend to sound the same. Whether the author decides to be poetic about it, or do the opposite and be as crass as possible, they’ll end up describing very similar features. With women it will be things like the plumpness of their lips, the curve of their bodies, or the silken flow of their hair. With men it would be more like the chiseled line of their jaw, the musculature of their frame, and so on and so forth.
When you are creating a character, it’s more interesting (not to mention more fun) to describe them by emphasizing what makes them unique, or simply what makes them human. If I crafted a character modeled after the man described above, I can promise that no one reading the story would forget what he looked like. It would be branded into their imaginations. This applies to psychological traits as well as physical ones. If the characters in a story are mentally unbalanced, arrogant, or just impulsive to the point of stupidity, readers respond to them better than if the characters are perfectly controlled, emotionally centered, and smart to the point of precognition. A character’s flaws anchor them in reality and make them distinctive and memorable, which is a good quality to have.