What are the problems that contributed to violence in the story?

In Edgar Allan Poe's "The Black Cat," the narrator attributes his violent behavior to alcoholism. He states that the first black cat, Pluto, was an especially beloved pet, but over the course of a few years, the "Fiend Intemperance" caused the narrator to become more violent and irritable day by day. Under the effects of alcoholism, the narrator becomes verbally and physically abusive toward his wife. He abuses "rabbits, the monkey, or even the dog." One night when he comes home drunk, he mistreats Pluto, who bites him. In a fit of "fiendish malevolence, gin-nurtured," the narrator cuts out Pluto's eye with a pen-knife. Even the realization of what drinking has led him to do does not keep him from going back to liquor. After hanging Pluto, the narrator takes on another cat  when he is "half-stupefied" from alcohol. 

While the narrator's "disease," alcoholism, sets his violent behavior in motion, once the second black cat comes to live with him, the narrator doesn't speak much of liquor as the cause of his temper and violence. Instead, it seems that the cat reminds him of his previous crimes, and those pangs of conscience lead him to give way to "the darkest and most evil of thoughts." He continues to abuse his wife. One day they go into the cellar, and there the cat "exasperated me to madness." With "a rage more than demoniacal," he buries the axe in his wife's head. In prison, awaiting death by hanging, he considers the "hideous beast whose craft had seduced me into murder." Now he is blaming his violence not on alcoholism, but on some supernatural ability of the cat to inspire his actions.

Ironically the narrator wants to blame alcohol, a disease, or the cat for his actions, but each step of the way the man chose to follow his lower instincts, even when he recognized the evil in himself, rather than take responsibility for his faults and seek to correct them. So the narrator's unwillingness to accept responsibility for his actions is what causes the downward spiral into violence and murder.