There are two main reasons Monte Cristo now doubts himself. What are both?

What makes Edmond such a fascinating, complex character is that at various points in the story he entertains doubts about exacting such terrible revenge on his enemies. One such example comes in Chapter 67 when he successfully destroys Villefort. Thanks to Edmond's machinations, Villefort loses absolutely everything. Not only does his legal career and reputation lie in ruins, but his wife kills their child before committing suicide. Though in the previous chapter Villefort had cruelly instructed his wife to kill herself, he wasn't expecting her to murder their son. It is all too much for Villefort and he goes completely out of his mind. Edmond thinks that perhaps he went a little too far in his revenge.
He reflects on Villefort again when he returns to the Chateau d'If, the former site of his incarceration, which is now a tourist attraction. As he walks around the old prison, Edmond starts to feel pangs of guilt over the death of Villefort's son. The child was wholly innocent yet still suffered as a result of his father's public exposure as a criminal. But then Edmond reminds himself of the immense suffering he endured as a result of Villefort's scheming and realizes that, all things considered, he did the right thing in taking revenge on him and his other enemies.