While he plays a crucial role in the story, Bard is primarily defined by his single defining characteristic: his skill as an archer.
* He is introduced as a master archer who can hit a target from afar, and this ability ultimately saves the town of Lake-town and leads to the defeat of Smaug.
* He is described as brave and resourceful, but his other qualities are not explored in much depth.
* His motivations are relatively simple: to protect his home and family.
While he does show some emotional range, such as grief and determination, these are mostly linked to his role as a protector and are not explored with much complexity.
Other characters, like the dwarves or even Bilbo, exhibit more complex personalities and motivations, making Bard stand out as a more straightforward, flat character.
Of course, the interpretation of a character's flatness is subjective and depends on the reader's perspective. Some might argue that Bard has enough depth to be considered a round character, while others might find his focus on archery and protection makes him a more one-dimensional figure.