Don John. He does a fine job of it, too.
As you know if you have ever seen the play, Claudio was supposed to be married to Hero, Beatrice's cousin, but when asked whether he would take this woman to be his wife, he said something along the lines of "That whôre! Not on your life!" and walked out, leaving Hero collapsing in shame and grief. She was reported dead not long after. Naturally this made Beatrice somewhat angry at Claudio, which is why she wanted him killed.
Hero
Don John got Borachio to make love to his girlfriend in Hero's bedroom calling her Hero all the while. Meanwhile Don John got Don Pedro and Hero's fiancé Claudio to stand under the window to overhear all this lovemaking and moaning of Hero's name. Naturally, Claudio could come to only one conclusion. It's hard to figure out why Borachio's girlfriend would go along with this, though. Or indeed why she doesn't speak up at the wedding.
Claudio Encarnacion Montero goes by Claudio.
I think that leonato's instruction to hero is to say yes to claudio if he asks to marry her and this shows that the traditional attitudes were to get married at a young age and to get money.
Don John was born out of wedlock, he feels like nobody deserves to live a happy life, or get married. Also, many people think that Don John actually loved Hero, so was jealous of Claudio;and felt like since he couldn't marry Hero, Claudio shouldn't be able to either.
He is bewildered at first and thinks that they must mean something else. But eventually he believes them and gets angry with Hero. His first reaction is to believe them and say his daughter is dead to him.
When Hero is publicly traduced by Don Pedro and Claudio, her friends and relatives react differently. Beatrice helps conspire to fake Hero's death, so she will not have to live with the shame. She also encourages Benedick to "Kill Claudio" and he accordingly challenges him to a duel. Leonato challenges Don Pedro. Once Claudio and Don Pedro are faced with the evidence that they have wrongfully accused Hero, Leonato forgives him but charges him with a penance. He also asks Claudio to marry his "niece" but, with the connivance of Beatrice and the other women, it is Hero who shows up at the altar.
Claudio
Hero and Claudio have problems, but they marry and are happy at the end.
Balthasar disobeys his master by revealing the plan to secretly marry Hero to Claudio, causing Claudio to publicly shame her at their wedding. Balthasar defies his master's orders to keep the plan confidential, which ultimately leads to significant consequences for Hero.
Hero has been unfaithful to Claudio.
He fools Claudio and Don Pedro into thinking that Hero was hooking up with another guy on her wedding night, causing Claudio to humiliate her and to refuse to marry her.
claudio speaks against hero
He has been told that since Hero is dead he must marry her cousin. This is who he thinks he is marrying although he is actually marrying Hero who is not really dead.
plead Claudio's case to Hero and Leonato.