The correct answer is William Shakespeare because Keats used the term "negative capability" to describe a specific quality in great writers, particularly in Shakespeare.
In Keats' view, negative capability is the ability to accept uncertainty, doubt, and ambiguity without the need for concrete resolution or logical explanation. He believed that Shakespeare exemplified this quality because his works often allow characters and situations to remain mysterious and open to multiple interpretations, without forcing a clear moral or intellectual conclusion.
Keats contrasted Shakespeare's "negative capability" with poets like John Milton and William Wordsworth, whose works he felt were more concerned with imposing personal convictions or seeking philosophical certainty.
Thus, Shakespeare is regarded by Keats as the prime example of this concept.