Is it possible to argue that Macbeth is the villain of the play and Banquo or Macduff it's hero? Substantiate with examples from the text.
In Act I Macbeth, Shakespeare shows the hero and villain conjoined. Unlike other tragedies, like Othello, where there is a clear division between hero (Othello) and villain (Iago) from the start, Shakespeare presents Macbeth as the ideal thane: "bloody, bold, and resolute." In Act I.ii, Bleeding Captain trumpets his praises before his first entrance:
For brave Macbeth--well he deserves that name--
Disdaining fortune, with his brandish'd steel,
Which smoked with bloody execution,
Like valour's minion carved out his passage
Till he faced the slave;
Which ne'er shook hands, nor bade farewell to him,
Till he unseam'd him from the nave to the chaps,
And fix'd his head upon our battlements.
Little Macbeth does over the course of the play that deviates from this description: he is violent throughout. It is only that his violence is misdirected, aimed at the King, that makes it immoral. But what if Duncan was an immoral or, worse, ineffective king? This equivocal morality shows the Machiavellian duality in Macbeth: his violence is divorced from allegiance to God and country. Macbeth uses violence for its opportunistic advance: "the ends justifies the means."
More, Macbeth is a kind of feminist hero as well. He is deferential to his wife, and his marriage--at least in Act I--is integrated (they share the decision-making). As they are focused on career instead of kids, the Macbeths are the modern uber-couple, shamelessly materialistic.
Macduff, the supposed hero of the second half of the play, is a foil and doppelganger of Macbeth: he was born bloody. He will decapitate Macbeth in the same way Macbeth guts and beheads Macdonwald. In fact, Macduff's violence is used against the state (he kills the King of Scotland), and it is motivated by revenge.
Banquo does little that is overtly heroic in the play. He seems the passive and inactive thane who contemplates fate and morality too long. Like Macduff, Banquo does not realize that he is a man of violence until his family is openly assaulted.
Both Banquo and Macduff have segregated marriages. Banquo has no wife at all, and Macduff does not listen to his wife's warning to protect his castle. He completely abandons her! Macduff, especially, comes from the old patriarchal culture that treats women as domestic servants and children as better seen than heard.
Both Banquo and Macduff foolishly underestimate the nature of their vocation. They see a thane as an old, romantic construction of ideals (honor, loyalty) instead of a violent and political agent. Their belief in the Great Chain of Being has deceived them in thinking the King is God's holy vessel, blindly to be followed, incapable of being toppled.
Macbeth is hero turned villain when it comes to these old beliefs, but he is one of the first great modern political and psychological heroes, paving the way for Machiavelli's Prince, Nietzsche's Superman, and Freud's id.
macduff nor banquo is the plays hero
but macbeth is the tragic hero
and also the villan