What is Don John's character profile in the play Much Ado About Nothing?

Don John is the villain of Much Ado About Nothing. By all appearances, he is sullen and quiet. When Leonato welcomes him into his home, Don John says that he is “not of many words.” Beatrice says that he looks so “tartly” she is “heart-burned an hour after.” She compares him to “an image [that] says nothing,” and Hero admits that he “is of a very melancholy disposition.”

The reason for his gloom is...

Don John is the villain of Much Ado About Nothing. By all appearances, he is sullen and quiet. When Leonato welcomes him into his home, Don John says that he is “not of many words.” Beatrice says that he looks so “tartly” she is “heart-burned an hour after.” She compares him to “an image [that] says nothing,” and Hero admits that he “is of a very melancholy disposition.”

The reason for his gloom is because he is the prince Don Pedro’s illegitimate brother. They have only recently reconciled, and Don John resents his position. He is also jealous of Claudio for stealing Don Pedro’s affection. Don John refuses to show any gratitude, stating that he will “smile at no man's jests” and laugh only when he is merry. He explains quite clearly how bitter and disagreeable he is:

I had rather be a canker in a hedge than a rose in his [Don Pedro’s] grace, and it better fits my blood to be disdained of all than to fashion a carriage to rob love from any: in this, though I cannot be said to be a flattering honest man, it must not be denied but I am a plain-dealing villain.

Don John and his friends devise a plot to shame Don Pedro, Claudio, and Hero, Claudio’s innocent fiancée. He first manipulates Claudio into thinking Don Pedro wants Hero for himself and then “proves” to Claudio and Don Pedro that Hero is having an affair with the drunkard Borachio. (It is actually Borachio and Margaret, not Hero, who have the liaison.) Don John’s cruel devices put a damper on the celebrations in Messina.