Rank Dantes' enemies from the most to least guilty and give evidence for the choices in The Count of Monte Cristo.
In terms of Dantes' enemies, the least guilty is Danglars, his fellow shipmate. Danglars is motivated by simple jealousy. He is unsophisticated, but his reason for turning on Dantes is totally self-serving, without the malice of forethought.
The next most guilty of Dantes' enemies is Villefort. One one-time prosecutor is interested in protecting himself and his political self-interests and aspirations. With Villefort, as with Danglars, it's nothing personal.
Enter Fernand. This is the most dangerous and most malicious of Dantes' enemies. He is jealous, as was Danglars, but his betrayal is the worst because he is Edmond Dantes' best friend. Edmond has little of worldly value, but he does have the love a woman who will have nothing to do with Fernand. Mercedes and Edmond plan to wed, and just as it seems Edmond's dearest wish to marry and settle down opens up to him, Fernand consorts to destroy Edmond.
If it's not bad enough to rob Edmond of the love of his life, he orchestrates Edmond's betrayal which robs him of the company of friends and family when he is imprisoned in Chateau d'If for many years.
Fernand seems motivated by nothing more than having what he cannot have, for he comes from a wealthy family, where Edmond has little to speak of in the world. Fernand, like a petulant, uncaring child, takes what he wants without concern for the consequences to others. His malice is what makes him Edmond Dantes' worst enemy.