Macduff was not born of a woman because his mother had a C section. The witches said no man born of woman could kill Macbeth.
In the last scene of MacBeth, MacBeth is killed offstage by MacDuff in their brawl. After their fighting goes off stage MacDuff returns to the stage with MacBeth's head. This event is very similar to the beheading of Macdonwald the traitor by MacBeth early in MacBeth.
Macbeth didn't think Macduff was a threat because the witches said "None of woman born shall harm Macbeth." Macbeth welcomes this good news and, assuming Macduff was born the natural way, Macbeth thinks he has nothing to fear.
After the banquet where Banquo's ghost appears, he tells Lady Macbeth that he "will send" so he hasn't done it yet. The next time we see him, he is visiting the witches, and then Lennox brings word that Macduff is fled to England. Macbeth says "Time, thou anticipat'st my dread exploits." What this means is that Macduff got away before Macbeth could get to him. It would seem that Macbeth never does send for Macduff.
Yes, in Act 3, Scene 1 of Macbeth, Macbeth learns that Macduff has fled to England to seek support against him. This news not only angers Macbeth but also fuels his paranoia and reinforces his determination to eliminate any threats to his rule.
Macbeth was responsible for the deaths of Macduff's entire family and household. In Act 4 Scene 1 of the Shakespearean play, he decided to kill Macduff. But before he could carry out his plans, he met up with the noble Scotsman Lennox. From that meeting, he learned that Macduff already had fled Scotland for England. So Macbeth changed his murderous plans. Instead, he decided to have everyone in Macduff's family and household killed. Among the victims of the Fife Castle massacre were Macduff's wife and son.
Macduff's comment about Macbeth having no children emphasizes Macbeth's lack of a rightful heir to succeed him as king. It signifies a disruption in the natural order and highlights Macbeth's guilt and responsibility for the chaos he has created. Moreover, it suggests that Macbeth's legacy will not continue beyond his own reign, further emphasizing his downfall.
At the start of the play, before meeting the witches, Macbeth is still loyal to Duncan. The forces of Norway and the rebel Macdonwald (whom he kills in battle) could be considered his adversaries at this point in the play. After he meets the witches and begins to entertain thoughts of regicide, anyone who stands between him and power becomes his adversary (Duncan, Malcolm, Banquo, Macduff...) One could probably make an argument as to why Lady Macbeth might be considered Macbeth's adversary as well.
Malcolm suspected Macduff of having designs on the crown and throne of Scotland. In Act 4 Scene 3, Macduff had arrived in England from Scotland. He had joined the group of discontented Scotsmen that had formed around the subsequent King Malcolm III [d. November 13, 1093]. Malcolm wanted to take the throne of Scotland away from Macbeth [c. 1014-August 15, 1057]. He wanted someone else to kill and behead Macbeth. But he didn't want Macbeth's murderer to gain the Scottish crown and throne. Malcolm knew that Macbeth had had Macduff's entire family and household murdered. So he wanted Macduff to be Macbeth's murderer. But he wanted to make sure that Macduff would do the killing only to avenge his lost family and household. He wanted to make sure that Macduff wouldn't try to claim the crown and throne as his.
He is the man not of woman born mentioned in the witches' prophecy, which is why they warned him to "beware Macduff". He is not born of woman because he was delivered by C-section. Apparently in order to be born you need to be born in the natural way.
"Macduff was from his mother's womb untimely ripp'd". According to the definition accepted by the witches, this makes Macduff not "born of woman" and thus not subject to the prophecy that none of woman born could harm Macbeth. It's a bit startling to us, since most of us think of people delivered by Caesarean section as being "born".
The "bloody baby" in Macbeth is a supernatural apparition that Macbeth encounters during the play. It warns Macbeth to be wary of Macduff, stating that Macbeth should fear him. The bloody baby is one of the many supernatural elements in the play that contribute to its dark and eerie atmosphere.