Claudio's Reputation
As mentioned, reputation is a central point of tension in the play. When audiences first meet Claudio, it is through his reputation alone – a messenger explains that he has defied all expectations of his youth by becoming an excellent soldier. However, as the play develops, it becomes clear that Claudio is still very much immature about love despite his military success. The initial image of Claudio presented by the messenger is therefore at odds with his character's behavior for the rest of the play.
Don John's Plan
Don John maliciously plots to destroy the relationship between Claudio and Hero and sully Hero's reputation. While the audience knows that this scheme is afoot and that the people having sex near Hero's window are actually Margaret and Borachio, the other characters believe that Hero has been unfaithful to Claudio, thereby destroying her good image. Her own father Leonato denounces her as well, emphasizing the extent to which characters' gullibility prevents them from seeing the truth about each other.
Hero's Death
After it comes to light that Hero is innocent, Beatrice and Leonato still maintain that she is dead in order to punish Claudio. The audience is well aware that Hero is still alive, but Claudio orchestrates an elaborate ceremony to bury his newly-innocent lover and restore her reputation before discovering that the "niece" he is to marry is actually Hero.
Benedick and Beatrice
Benedick and Beatrice are two characters who purport to hate the other gender and despise marriage throughout the play. In a predictable but ironic development, they fall in love with one another and are married in the final act.