The final stanza in "The Raven" is a particularly important one, for several reasons. First of all, the stanza is important because it is the last one, which means that it is the stanza that provides a sense of closure to the reader. However, this closure is not absolute. We see that the author changes the tense of the verbs to describe an action that is still happening at present ("And the Raven, never flitting, still is sitting, still is sitting"). This gives the stanza a particular vividness and relevance.
Moreover, the last stanza relies particularly heavily on repetition. Although this was employed in other cases throughout the poem, at this stage it gives the reader a sense of inevitability, as the opportunities for change and redemption are over. Finally, the stanza employs the word "nevermore" again, but this time it does so with an exclamation mark, leaving a lasting impression on the mind of the reader.