It seems to me that one of the essential points in writing a thesis paragraph on a specific death scene is being able to link the scene with the thematic purpose of the work. The paragraph would consist of an opening sentence that would serve as a topic sentence or a sentence which would clearly state your thesis. In this case, linking the specific death scene to the thematic purpose of Things Fall Apart. The subsequent sentences in the paragraph would substantiate how this scene was important to the work, as a whole, and then how this death reflects the themes in Achebe's novel. The concluding sentences would confirm the link that has been explained. There is not a plot summary or detailing anything other than the death scene and its connection to particular themes in the novel.
One of the most profound themes that Achebe explores in Things Fall Apart is how betrayal is a significant part of what it means to be human. The world that Achebe shows is not one where solidarity is an absolute given in the human experience. This theme is underscored with Okonkwo's death and the death of the messenger which precedes it. I think that using this paradigm of both deaths as an example of the theme of betrayal in Things Fall Apart might be quite effective.
In Chapter 24, Okonkwo clearly recognizes that the Umuofia he has envisioned in his own mind is no longer present. This conception has "fallen apart," something that is shown to be evident in the reaction that the villagers have towards Okonkwo's murder of the messenger. At the moment when Okonkwo was convinced in the rallying cry of his actions, he instead comes to see the full force of betrayal that had always been a part of his life:
Okonkwo stood looking at the dead man. He knew that Umuofia would not go to war. He knew because they had let the other messengers escape. They had broken into tumult instead of action. He discerned fright in that tumult. He heard voices asking: 'Why did he do it?'"
The question of "why" is what causes the villagers to move away from him. The strength and vision of masculinity that he had come to define his own sense of self for so long was no longer intact. The decisive austerity with which he acted, one that had generated so much in way of status and respect from others, now resulted in "fright." Okonkwo realizes that he stands alone, and that the village will not support him in what he did or who he is. He is estranged and alone from both the village and the notion of self that he saw in the eyes of others. Okonkwo realizes at this moment that he is alienated and abandoned.
In Chapter 25, Okonkwo's death is not as much as a surprise as much as it is a logical extension. His suicide is the ultimate statement regarding the betrayal amongst human beings. He kills himself because he is unable to function in a world where his constructions of strength through solidarity are no longer honored. The world he once knew has "fallen apart," and Okonkwo is unable to live amongst its pieces. When he kills himself, the villagers do not honor him. Rather, they are afraid to touch his lifeless body because of the sin he has cast against the Earth. The villagers' reactions to Okonkwo's death confirms the Commissioner's belief that they are "primitive," something that he sees Okonkwo as. No longer the towering figure of strength and honor, Okonkwo has become marginalized as a "savage" who is capable of only being "pacified" and subdued. No one stands by Okonkwo, even in death. He is alone, the victim of betrayal. The extinguishing of the "Roaring Flame" in both death and public reaction represents the betrayal that Okonkwo experiences. He becomes the ultimate victim of cultural collision through the abandonment he experiences at his moment of need.
A thesis paragraph can be built around Okonkwo's death and the death of the messenger that brought it about. This death scene is representative of the theme of betrayal that is intrinsic to Achebe's work. Once Okonkwo takes action in killing the messenger, he believes that others will rally around him and make a defiant stand against the Europeans. The reality is that they turn away from him. They question his use of violence, a condition that once brought him great praise and stature from these same individuals. The betrayal and abandonment he experiences as reactions to his actions cause him to recognize that there is no structural center for him, no center of being. This helps him to embrace suicide. Exploring how betrayal helped to bring about Okonkwo's death and how the reaction to this was even more betrayal reflects how a particular death scene can embody a theme from Things Fall Apart.