Truly what is the most important aspect of an essay?

It is the thesis. Without a clear thesis and rationale set up for the essay the writing will lack the clarity and the main focus of the writing. Also another aspect needed to have a strong essay is having supported examples that back up your claims in the essay. D2's essay was by far the strongest out of all the essays I read because the writer emphasizes that Mr. Hurst is the epitome of triviality of Austen's aristocracy and, while also claiming wealth should not be the sole indicator of one's worth in society. D2 uses strong quotes to back up these claims in a way that also makes the reader ponder about the society in the novel as a whole.