All great (and even not so great) works of fiction have flawed characters. It is especially important that the narrative's protagonist be flawed. Without a character flaw, there is nothing for a character to overcome. As humans, we are all flawed creatures. Consequently, it is nearly impossible to identify with a character that is flawless. Character flaws can range from minor, to major, to tragic. Minor flaws are small idiosyncrasies that don't have a strong impact on the story. Rather, they make the protagonist accessible and set them apart from the rest of the film's characters. (Remember, Western cultures put a high value on individuality). Major flaws are more central to a character's struggle and become defining themes of a story. A tragic flaw is a trait that brings about a hero's downfall, and often leads to the character's death. In other cases, the "downfall" comes early in the story, and the hero performs some act of redemption later on.
An example of a tragic hero in film is Anakin Skywalker, from the Star Warsseries. In Star Wars: Episode III - Revenge of the Sith(2005), he dreams that his wife, Padme, will die in childbirth. He is consumed by fear and anger at this prospect. In order to save her, he turns to the Dark Side of The Force, known as "The Sith." As Padme gives birth, the knowledge that Anakin has turned to the Dark Side causes her to give up--to dye of a broken heart. Anakin, overcome by anger (and believing that he accidentally killed Padme and their unborn child), becomes the heartless, evil Darth Vader. (See 0:00 - 1:45 and 6:40 - 9:20 in the video on the left for the moments of downfall). In Episodes 4-6, Anakin continues on his evil path. At the end of Star Wars: Episode VI - Return of the Jedi (1983), Anakin rejects the Dark Side in order to save his son, Luke. This final act of redemption, and the death that follows, brings his character full circle. (The entire scene in the video on the right is fantastic, but skip to 6:00 for the moment of redemption).
Anakin's fall and rise takes place over the course of six films. For the purpose of this site, Simba's transformation in the 89 minute film, The Lion King(1994) is far more manageable. The film uses elements of Hamlet, a play about a tragic character, but Simba's story ends in a much more uplifting, kid-friendly manner. As a young cub, Simba's character flaws are embodied in the famous song, "I Just Can't Wait to Be King." Simba demonstrates ambition, pride, and disobedience in this scene. However, looking deeper into Simba's motivation, we see that his true "flaw" is a feeling of inferiority. He lives in the shadow of his father, and constantly strives to prove his worth by trying to be brave. Central to this flaw (and to the audience's connection to Simba) is Simba's relationship with his father. Simba's feeling of inferiority, combined with the feelings of guilt surrounding Mufasa's death, cause Simba to run away and reject his place as king.