It is in Chapter Two that Okonkwo's character is further explored, and in particular how his anger and rage is a direct response to his fear of resembling his father, who was gentle and lazy. Okonkwo, the text states, was so prone to responding to everything in anger because of the root fear that lurked deep within him that he might come to develop some of the characteristics that made his father such a weak and pitiful character. Note what the text says:
And so Okonkwo was ruled by one passion--to hate everything that his father Unoka had loved. One of those things was gentleness and another was idleness.
This is why his wives live in "perpetual fear of his fiery temper" as he seems to be governed by anger alone. Okonkwo is a character who is so ashamed of his father and the kind of man that he was that he has set himself against everything resembling his father and determined to be the opposite. This is why he is so angry all the time, because his father was so weak.