It’s never really clear what a “dimension” is for a fictional character. Many scholars have tried to give meaning to this word and each of them came out with a different definition. The only this that all those definitions have in common is the fact that “dimension” is not something physical, it actually has to do with the psychology of the character: his personality, his problems, his goals, his relationships etc…
According to Robert McKee, the author of the famous book Story, a dimension is a contradiction within the character’s personality and this contradiction determines what choices the character will take.
So, following this logic we can say that the more “dimensions” a character has the more interesting his personalitywill be, but that doesn’t mean that we can give for discounted that a character with only one dimension is boring. Because one dimension (two conflicting personality traits) in the hands of the right writer might be enough to create a compelling story.
Here’s how the character Maui, from the Disney movie Moana (the figure from the Polynesian mythology is completely different), can be considered two dimensional.
