How are both Things fall Apart and Death and the King's Horseman examples of tragedy?
The Renaissance Shakespearean definition of a tragedy revolves around a good and moral hero who is much to be admired but who has an iner flaw in his character traits or who makes an unintended error in judgement. The definition is a drama in which the hero's fatal inner flaw or fatal error in judgement leads to circumstances so terrible that the only possible outcome is the hero's death. [Greek tragedy does not require the hero's death in the end.]
In Things Fall Apart, Okonkwo has an inner flaw in his character traits. He has only a mediocre chi, the "god force" within him and the resulting weakness make him imbalanced between both female qualities of kindness and male qualities of assertiveness. As a result he thends to choose violence as a means of controling his family and this choice for ciolence accidentally displays itself through accidents in the village, like when his gun explodes and kills Ezeudu’s son. In the end, the troubles Okonkwo causes because of his inner fatal flaw must and do result in his death.
In Death and the King's Horseman, the hero Elesin makes a fatal error in judgement that delays his ritual preparations for his ritual death that will allow him to accompany his dead King in the King's burial and journey through death. As a result of Elesin's distraction and delay, the colonizing British officials here of the impending ritual death and determine that, since ritual suicide violates British law and would therefore cause trouble while the English Prince is visiting, they will stop the ritual. Elesin is duly arrested and prevented from carrying out his duty and imprisoned. A great tribal wrong is thus committed because great consequences rest on the fulfillment of the ritual.
To rectify the wrong Elesin's son acts as substitute and slays himself in his father's place at which Elesin finds a way to slay himself in his prison cell in order to join son and King. In the end, Elesin's fatal error in judgement leads to his death after first causing the death of his son.