The best part of the book remains the time in prison. Then it hits a bit of a lull. The best "revenge" moment is with Fernand, where the final blow is not dealt by the Count but by the reveal of the full extend of Fernands guilt towards him:
When Fernand comes to the Count, demanding to duel, in a way he must feel kind of "liberated". In spite of all the bad things he's done in his life, here is a man, the Count, who has wronged him so much that it appears to Fernand that he is finally in a position again to defend himself righteously as the innocent man.
>“Oh,” cried the general, as if branded with a hot iron, “wretch,—to reproach me with my shame when about, perhaps, to kill me! No, I did not say I was a stranger to you. I know well, demon, that you have penetrated into the darkness of the past, and that you have read, by the light of what torch I know not, every page of my life; but perhaps I may be more honorable in my shame than you under your pompous coverings. No—no, I am aware you know me; but I know you only as an adventurer sewn up in gold and jewellery. You call yourself, in Paris, the Count of Monte Cristo; in Italy, Sinbad the Sailor; in Malta, I forget what. But it is your real name I want to know, in the midst of your hundred names, that I may pronounce it when we meet to fight, at the moment when I plunge my sword through your heart.”
– this being in response to the Count recounting the life and deeds and crimes of Fernand. Then Monte Cristo reveals himself by changing clothes to appear again as Edmond Dantès, at that moment removing the only footing the General had left to stand on after his life fell into ruins – a righteous quest for revenge – and leaving suicide his only option. Best revenge moment in all of literature.
Of course the entire journey of the Count is morally objectionable as the results show us, but this moment still strikes me with how well it's executed.