Depends on how major a character they are. If they are a main character and play a pivotal role in the story, they must be pretty complex - or at least complete. Some people are just naturally not complex, and as long as the character is balanced and believeable that's fine. Minor characters don't need as much complexity, but they must have a motive for doing whatever they're doing.
A round character has many traits, some of which may even be contradictory--a very complex individual
A complex character is a type of character that is more than one-dimensional. He/she changes attitudes and behaviors to suit different situations.
Mathilde from The Necklace is complex because she is not a one dimensional character. She is a round character who is not stereotypical and struggles with her own motives.
The character experiences many different emotions and has multiple motivations.
This is a "round" (complex) character.
This is a "round" (complex) character.
A complex character can be called many things. Believable and realistic are two words, but perhaps you are thinking of "round" characters as opposed to "flat" characters who are not complex.
A character who shows different sides
round character
Round character
A polygenic character is influenced by multiple genes, each contributing in a quantitative manner to the phenotype. A complex character refers to traits influenced not only by genetics but also by environmental factors. While a polygenic character specifically focuses on the contribution of multiple genes, a complex character includes additional influences beyond genetic factors.
protagonist