The father and son are almost completely antithetical in personality type, in world view, in interests, and in accomplishments and status. Unoka is calm, lazy, and given to laugher; Okonkwo is intense and jumpy, driven and workaholic, athletic, and prisoner of his own temper. Unoka embraces the moment, while Okonkwo embraces the future. Unoka loves music and companionship, while Okonkwo values hard work and its fruits, yet never enjoys them the way Unoka can. Finally, Unoka is known as a debtor and a weakling in his clan, unable to pay any debts and laughing them away, and he dies with dishonor (especially in Okonkwo's eyes). Okonkwo gains land, three wives, and has several children; he owes no one by the time he is a mature adult. He has status in the clan for not only wealth but his physical accomplishments as warrior and wrestler. He has achieved way beyond his father, in terms of how the clan defines achievement. However, he is man to be feared by all his wives and his children.
These two men personify antithesis.
The first two chapters of the novel help establish these differences, and I recommend that you study those closely for specific instances (such as the scene where Unoka says he cannot pay back his debts, and laughs it off and the listing of Okonkwo's accomplishments).
The question is, does the antithetical positioning that Achebe establishes ask us to empathize with one character over another, with both, or with neither? Why?