In Chapter IV Dantes remarks that happiness can only be attained "by overcoming "dragons [that stand over one's happiness]...." The dragons that intervene between one's happiness and one's fates are each person's character flaw.
The fates of each character, then, depend upon whether they are able to conquer the dragons of their character. For instance, Danglars's flaw is his avarice; failing to conquer his greed, he rejects his wife who has lost sums of money; he seeks to regain money even if it means selling off his family member. As a result, he loses what really matters: family and his life.
Similarly, de Villefort loses his family because of his dragon: He seeks power even if he must hide his Bonapartist father and bury his illegitimate son in order to maintain a prestigious reputation. Because of his deception, he is exposed by Dantes, with tragic results.
Fernando's desire to attain prestige and military position leads him to kill and to betray the trust and love of a Middle Eastern king. His dragon of treachery turns itself on him and he, too, is exposed as the "hyena" that he is.
Only Edmund Dantes overcomes his dragon, his desire for revenge. He, then, is redeemed by saving the Morrel family and helping a young couple save their love.
Edmond Dante - is redeemed finding his own revenge too much to handle. He sets some things right and finds love with his ward, Haydee.
Mercédès Mondego - leaves her husband and retires to Marseille. She wishes only for her son's happiness and asks nothing more of the Count but that.
Albert Mondego - along with his mother abandons his father as well as his name. He does not stay in Marseille with his mother, but instead goes out to seek his fortune. He is going to Algeria to see if he can become an officer and thus find some honor for himself.
Fernand Mondego ( Count de Morcerf) - commits suicide after having been confronted by the evidence of his number nefarious acts and being abandoned by his wife and son.
Baron Danglars - abandons his wife, attempts to sell his daughter into a marriage for profit. He is eventually forgiven by the Count when he expresses sorrow for what he has done and asks forgiveness.
Gérard de Villefort- the prosecutor who send Edmond to prison to protect his political aspirations eventually protects them by giving his second wife the choice either to kill herself or be denounced and arrested for murder. Although he tries to stop her, he is too late. In the end, he goes insane with grief.
Héloïse de Villefort - the second wife of Gérard de Villefort seeks to protect her son and his inheritance through murder. she kills herself and her son.