In Much Ado About Nothing, what are some examples of gullible characters that make bad decisions or take rash actions?
As is frequent in Shakespeare's work, many of the characters are easily fooled in this play. Deception is neither good nor bad in every case; sometimes it is destructive, while sometimes it is wonderful.
Beatrice and Benedick are tricked into following in love with one another when Don Pedro and his friends hatch their plot to bring the couple together. The two falling in love may be rash, but it ends up being great for the couple. Hero's gullibility is also good at times. Don Pedro convinces her that he is Claudio, which allows him to bring the two young lovers together. Both of these gullible characters are tricked into doing something that makes their lives happier.
Trickery has a dark side in the play too, however. Don John tricks Claudio into believing that Don Pedro wants Hero for himself, and later even convinces him that his fiancee has been unfaithful. This causes him to condemn Hero on her wedding day, which causes a rift between the characters in the play. Hero loses Claudio and Beatrice demands that Benedick kill Claudio. The damage is only undone by yet another case of deception later in the play.
Deception is a key theme in Much Ado about Nothing and in Shakespeare's work overall.