At first reading, The Count of Monte Cristo seems a novel of revenge, but upon a second reading, one realizes that while Emund Dantes does exact retribution upon his enemies, a main theme is one of redemption.
Always in Dantes there is goodness; he does not forget those who have shown kindness to him or to his dear father. As soon as he acquires a fortune, Dantes, as Sinbad the Sailor, fills the red purse in which Morrel put money for his father with payments to keep the family going after the loss of their ships. He rescues Albert de Morcerf from the bandits, and when he has the opportunity to kill Albert in a duel, he does not out of his eternal love for Mercedes. Dantes always is the protector of Maximillan, son of Morrel. In a very telling passage, Dantes instructs Maximillen,
here is the secret of my conduct to you: there is neither happiness nor unhappiness in this world: there is only the comparison of one state with another. Only a man who has felt ultimate despair is capable of feeling ultimate bliss. It is necessary to have wished for death, Maximillien, in order to know how good it is to live.
With more heroic actions, Monte Cristo saves Valentine de Villefort from dying at the hands of her stepmother. He rescues her and brings her to the despairing Maximillen Morrel, restoring the two lovers. The novel ends as Valentine tells her paramour,
Darling,...has not the count just told us that all human wisdom was contained in these two words,--'Wait and hope'?
Through his loving and heroic actions, Edmund Dantes, the Count of Monte Cristo, redeems himself even if he does deal retribution beforehand, demonstrating that he has learned much from the Abbe Faria.
To me, one of the most defining features is the amazingly cruel and devious methods of revenge that Edmond takes on those who have wronged him. He doesn't do anything simply nor does he allow people an easy death or simple ruination to get them out of their guilt. He makes people twist their own actions to lead to their own death or the death of their loved ones. He drives them insane by having their entire lives fall apart around them. Nothing is out of bounds with this guy.
Another, in my mind, is the fact that he does not end up with Mercedes in the end. Though he doesn't view her as an enemy, he cannot forgive her and allow himself to feel what he once did for her, an interesting change in the normal plot of a revenge story.