The novel's protagonist, Okonkwo, epitomizes what we would now call toxic masculinity. As he has antiquated ideas when it comes to gender roles, Okonkwo firmly believes that men should be powerful, dominant, and at times even cruel if they are to fulfill their traditional roles and command the respect of everyone.
Okonkwo is by no means alone in displaying such attitudes. To a large extent, they are a product of his culture and upbringing. The problem, however, is that he takes them too far, causing suffering to others as well as bringing him a lot of trouble.
Okonkwo has become so rich and powerful that he sees no reason to change his ways or his outlook on life. Having already associated masculinity in his mind with aggression, he is already predisposed toward violence, even when an alternative course of action is available. In that sense, Okonkwo departs from the traditions of his tribe rather than doing full justice to them.
The consequences are dire. Okonkwo regularly beats his wives, even threatening to kill them. He ends up killing his adopted son, Ikemefuna, and accidentally kills a man from the village. It is the latter of these two actions that causes the most difficulty for Okonkwo, as it leads to his being exiled.