There are a few things that come to mind. There's poorly written and poorly structured. The latter is a one-dimensional character, one who alters irrationally or randomly and serves the narrative rather than the tale. Also, there are characters who are just plain stupid.
Badly written characters are those that suffer from poor word choice and sentence structure. Often times these characters will be one-dimensional, which can be defined as a character who alters their behavior irrationally or randomly for no reason other than to move the story forward. Sometimes characters who are simply stupid can ruin a book.
The worst kind of writer is one who thinks they're not allowed to use adjectives or adverbs...or both at the same time! Adjectives describe a person or thing without saying so outright; adverbs affect the way someone or something acts, said person or thing being implied by the adjective/adverb combination. For example, "a tall, dark, and handsome stranger" is an adjective-adverb combo used to describe someone good-looking. Words like very, completely, always, never, and equally are common adjectives and adverbs.
Avoid using words that only conjure up visual images. This includes words such as huge, small, long, short, white, black, old, and new.
Characters are typically used by authors to advance the tale along a plot line, as well as to conduct acts and deliver dialogue. A tale might feature a single character or a protagonist while yet telling a larger plot. The character's dispute might be an internal one with himself or herself. Or it could be an external conflict such as fighting off an enemy or confronting physical adversity.
Internal conflicts are those within the character himself or herself. This could be a struggle between good and evil, right and wrong, strength and weakness. It can also be a battle of self-doubt vs confidence. An example would be a young boy who wants to go out for football but is afraid he will fail. He might debate whether or not he should try out for his school's team. This would be an internal conflict for him since he has to make a choice: risk failure or stay safe and sound at home. In the end he decides to try out and succeeds in making the team which shows that he overcame his fear.
External conflicts are those between the character and another person or thing outside of himself or herself. This could be another character who wants to harm the main character, a monster who needs to be fought off, or some form of physical adversity such as weather conditions or dangerous situations. External conflicts often give rise to stories because they are interesting topics that can be explored from many different points of view.
Characters are the lifeblood of any tale. Most authors will tell you that a character arc is crucial to producing a successful novel, just as most people would tell you that a story requires a beginning, a middle, and a conclusion. Of course, as with the last guideline, there are always exceptions in art. But generally, characters must progress through some sort of arc before the book can be considered complete.
What is an arc? An arc is a gradual change over time, usually involving a struggle between good and evil, light and darkness, etc. The term is also used to describe the trajectory followed by a character as she or he progresses from one stage of life to another. Every character should have an arc; some characters more than others. A character sheet can help you identify which characters might be lacking in an arc system. For example, a character who starts out as evil and then becomes good over the course of the story would not have an arc because his or her status quo never changes.
There are two types of arcs: internal and external. For example, when Romeo loves Juliet, he sees things about her that other people don't even know exist. This shows that he has an internal arc - he grows throughout the course of the story. External arcs are what make characters distinct from each other. They show how a character reacts to situations outside of himself or herself.
Characters must appear real in order to captivate and move readers. Authors do this by including details that distinguish and distinguish characters. Characterization provides readers with a clear feeling of the characters' personalities and complexity; it brings them to life and makes them vibrant, living, and credible.
The goal of characterization is for the reader to feel like they know the character, which means an author needs to give them some way to identify with them. This could be something as simple as sharing their fears or desires with the character. The more an author can do to make their characters unique, the more interesting they will be.
There are many ways to characterize characters. You can describe their physical appearance, such as "a tall man with dark hair and eyes" or you can talk about their personality traits, such as "he was a friendly guy who loved jokes". Either way, you need to include enough information for the reader to understand who the character is and how he or she differs from others.
In addition to describing their physical attributes and actions, authors should also consider how they would sound if someone spoke directly to them (i.e., voice quality). For example, if one character speaks with a British accent while another has an American one, then an author would need to use this information when writing their story. A reader might not realize it, but without this detail they would be unable to accurately interpret what each person said.
A satisfied character will not mix things up and create an intriguing scenario. Characters are intriguing because of their choices. When authors first start writing, they may conceive an interesting location or circumstance and then insert an Everyman sort of character into it to convey it to the reader. However, more often than not, they soon realize that this character is just not very dynamic or compelling. To make a character more interesting, give him or her goals beyond simply surviving the story.
An interesting character is one who exhibits variety. A character can be interesting even if he or she does not change over time. For example, Antony from Shakespeare's Julius Caesar is an interesting character because he is consistent in his beliefs about how others should behave toward him. He does not change his mind when presented with new information or situations. An interesting character also tends to be flawed; we can understand why he or she would act in ways that are contrary to his or her values.
Finally, an interesting character is memorable. This might seem like a trivial point but it isn't. We remember characters who exhibit variety, consistency, and clarity of purpose. If you want your character to stand out from the crowd, give him or her some traits that make them unique.
As you can see, an interesting character is a combination of traits that produce a person who is satisfying to read about.