Like his fellow convict Benedetto (a.k.a. Andrea Cavalcanti), Caderousse certainly knows how to waste a golden opportunity. Caderousse was never perfect – he was a drunk, and a coward, and less then scrupulous when it came to money – but he was also never active in sticking it to Edmond.
So it makes sense that a certain Abbé Busoni (a.k.a. the Count of Monte Cristo) would come visit Caderousse with a gift: a nice little diamond. And what does Caderousse do with it? Well, he tries to kill the man he sells it to in order to double his money. Then ends up getting arrested.
Oddly enough, Caderousse is the first of the Marseille Four – Danglars, Fernand, and Villefort being the other three – to die. (How else do you explain the Count's exclaiming "One!" right after Caderousse dies?) The real takeaway from the former tailor's death is tied up in his reaction to death. When the Abbé Busoni, who rushes to the dying Caderousse, suggests that his murder is all part of God's plan, Caderousse is indignant; "I don't believe in God!" he says. When the abbé reveals his true identity, however, he immediately changes his mind and asks God for forgiveness. Thus, Caderousse's death helps to confirm the Count's standing as the messenger of God – a standing that will, nonetheless, be called into question by book's end.