Benedick is from Padua in northern Italy. He's a soldier in the prince's regiment and a close friend of Don Pedro himself. Benedick is older than Claudio and is a self-avowed bachelor. He is known as something of a ladies' man but swears never to marry as he believes women are incapable of remaining faithful to their husbands. He has a quick wit and a silver tongue, and his friends and acquaintances look to him for a hearty laugh (often at his expense). Benedick is in a constant war of words with Beatrice, with whom he has been romantically linked in the past. Despite his promise to never marry, he finds himself falling in love with Beatrice after hearing she is in love with him. His affection for her is tested after Claudio slanders Hero, and Benedick proves his love for Beatrice by siding with the wronged woman instead of his old friends.
Beatrice is an orphan and under the guardianship of her uncle, Leonato. Though she is of noble blood and resides in the governor's home, Beatrice does not fit the mold of the traditional Elizabethan woman. Opinionated, outspoken, stubborn, independent, and full of wit, she declares herself averse to love. She is deeply distrustful of men, Benedick in particular. They have a long, unspecified history together, and the reader eventually learns Benedick broke Beatrice's heart. When the play begins, Beatrice seems interested only in insulting Benedick at every opportunity, but she softens at once when she overhears Benedick loves her. She quickly acknowledges she loves him in return.
Claudio is a young soldier from Florence, Italy, who earned Don Pedro's praise and friendship during battle. He returns to Messina with a heart open to love and finds it in Hero. Claudio's youth marks him as both rash and insecure. He is quick to want to marry Hero and even quicker to cast her aside, believes rumors from untrustworthy sources not once but twice, and neglects every opportunity to ascertain the truth. Threatened by Hero's alleged infidelity, he not only calls off the wedding, he publicly shames Hero to make himself feel superior. He shows no remorse upon Hero's "death" until he learns her slander was part of a nefarious plot orchestrated by Don John. Only then does Claudio feel bad for what he has done to his so-called true love.
Don Pedro is the Prince of Aragon. As such he is the person of highest rank in Much Ado About Nothing. Though he does not end up with a wife at the end of the play, he considers himself to be something of an expert lover as he woos Hero for Claudio and offers himself as husband to Beatrice. As a leader his greatest fault is his innate loyalty to those who may not deserve it. Instead of believing Hero's claims she is innocent, he believes the word of his brother, with whom he only recently reconciled after a bitter feud. Don Pedro also falls victim to his own vanity when his perfect match is called into question and, with Claudio, he ensures the destruction of Hero's reputation.
As the governor of Messina, Leonato is used to being in charge of not only his family but his city as well. Don Pedro's arrival changes the hierarchy of power. Though Don Pedro does not rule Messina, Leonato often defers to him out of respect for his title and his status as a guest. They have a friendly relationship until Hero's virtue is called into question. Leonato then breaks with social norms and supports the word of his daughter, a woman, rather than that of the high-ranking prince. He is more loyal to family than he is to power.
Don John has been marked as inadequate since birth because he was the product of an illegitimate relationship. He and Don Pedro, his half brother, have only recently mended their broken relationship when the play begins, and it is soon clear that Don John's part of the reconciliation was superficial at best. He knows he will never be as good as his brother the prince, so he decides to not even try and becomes a self-proclaimed villain. He's not even very good at that. He relies on Borachio to come up with and execute the plan to prevent the wedding between Claudio and Hero. He skips town when the deed is done, which is the next closest thing to admitting his guilt. He is caught at the play's end, but his punishment remains unknown.
Hero embodies the traits of what is often presented in classic literature as being the feminine ideal. She is modest, reserved, chaste, and happy to defer to her father's guidance. Hero is younger than Beatrice but old enough to marry. She is initially prepared to accept a proposal from Don Pedro, but she seems just as happy to be engaged to Claudio instead. Hero is unable to prove her innocence when accused of having a romantic relationship with a man other than Claudio. Instead of fighting back, she lets others take the lead in restoring her reputation. Hero still wants to marry Claudio despite the shame he brings upon her, which is a sign of both her forgiving nature and her acceptance of letting men run her life.