In Moby Dick what was captain ahab's weakness?

Captain Ahab's weakness was his obsession with the white whale. He was willing to endanger his life and the lives of his crew to harpoon the whale. He ultimately dooms them, in fact, as well as himself. His obsession with revenge for the whale maiming him leads to his death--he is caught around the neck by his harpoon rope, and the whale drags him into the sea. There is also irony in the fact that he is killed by his own harpoon, and it is a symbolic sort of death. The whale kills the crew and sinks the ship as well.

One could argue that this tragic flaw makes Ahab a tragic hero.