Who dies as a result of Macbeth's latest decree? Why are these murders more horrific than the previous one?
After Macbeth murders Duncan, he experiences a great deal of guilt, and he worries quite a bit about the consequences of his action. Once he has become king, however, he realizes that he is still not happy because he doesn't feel secure in his position: the Weird Sisters promised that Banquo's issue would be kings. Macbeth says, "To be thus is nothing / But to be safely thus" (3.1.52-53). In order to be "safely thus," he orders the murders of Banquo and his son Fleance. This is more horrific than Duncan's murder (which takes place off-stage) because it involves the attempted murder of a child and because it happens on stage, in full view of the audience. To watch a murder on stage is far more horrifying than it is to only hear about a character committing a murder.
Furthermore, when Macbeth learns that Macduff has fled Scotland and is out of his reach, he determines to kill his family: Macduff's wife, children, and even his servants. These are the most horrifying murders of the play because they happen on stage, they include the murder of an innocent mother and her babes, and because Macbeth has absolutely nothing to gain by it. He killed Duncan to get the crown; he ordered Banquo's murder to try to secure his position; however, there is no real reason for Macbeth to kill Macduff's family other than to be cruel and display his power.