What are the main conflicts in Macbeth act 4 scenes 1-3?
In act 4, scene 1, the first apparition conjured by the Weird Sisters tells Macbeth to "Beware Macduff! / Beware the Thane of Fife!" (4.1.81-82) The second apparition likewise mentions Macduff, and the danger he poses to Macbeth, although Macbeth does not realize this until much later in the play. This apparition says, "Laugh to scorn / The power of man, for none of woman born / Shall harm Macbeth" (4.1.90-92). Ultimately, Macbeth learns that Macduff was brought into the world via Cesarean section rather than by a natural birth. Therefore, Macduff was not, in the strictest sense, "born." At first, Macbeth decides that he has no need to fear Macduff as a result of this second prophecy, but he then decides to "make assurance double sure" and kill Macduff anyway. This scene's most prominent conflict is thus between Macbeth and Macduff.
In act 4, scene 2, the most prominent conflict is between Lady Macduff and her husband, Macduff, who she views as a traitor because he "abandoned" his family in England while he went to go fetch Malcolm home from England. She tells her son that his father is "dead" because that seems more honorable than it does to have a traitor for a father.
In act 4, scene 3, we see Macduff attempt to persuade Malcolm, who has taken refuge in England, to come home and fight Macbeth. However, the Thane of Ross comes to tell Macduff that Macbeth has had his entire family murdered: "Wife, children, servants, all that could be found" (4.3.249). Macduff then vows to kill Macbeth, saying, "Front to front / Bring thou this fiend of Scotland and myself. / Within my sword's length set him" (4.3.272-274). Thus, this scene's most prominent conflict is the one between Macduff and Macbeth.
Macbeth (unnatural) vs. the Witches (supernatural, fate, time): Macbeth wants to know the worst news from the worst sources. He certainly in abusing their prophecies and subverting nature and time in an attempt to retain power.
Macbeth vs. Macduff: the witches prophecies tell him to "Beware Macduff." Later, after Macduff hears of his family's death, vows revenge. This foreshadows the duel in Act V.
Macbeth vs. the Macduffs: Macbeth attempts to kill Macduff and his entire family. Macbeth has now killed innocent women and children.
Lady Macduff vs. Macduff/son: she calls her husband a coward for abandoning them. Macduff, not present, has fled to aid Malcolm in England. Later, after Malcolm tells him he was just testing him, they will have the first (*and only*) honest conversation in the entire play.
Malcolm vs. Macduff: Pretending to be as cruel as Macbeth, Malcolm questions Macduff as to his loyalty to Scotland.