Who was betrayed in Shakespeare's Macbeth and why?Name the characters and who betrayed them and the reason why they were betrayed.

Betrayal is a huge part of Macbeth.
The play opens with a battle that is being fought because two of the Thanes (Lords) who
are supposed to be serving King Duncan have turned against him.  In the first act of the
play, he has put down the rebellion.

So, in this opening of
the play and throughout the rest of the play, betrayal is motivated by a desire for
power, to gain status, and for Macbeth, the central figure who betrays many, the desire
to become and remain King.

Macbeth betrays King Duncan (to
whom he has sworn allegiance) by killing him when he is a guest at his home.  Why?  To
gain the crown that Duncan wears.  He also betrays his friend Banquo. Why?  To retain
the power and position of being King.  The witches had prophesied that Banquo's children
would be kings, and Macbeth wants to prevent this by killing Banquo and his son
Fleance.  He misses Fleance, but gets Banquo.

And you could
also make a case that Macbeth betrays Macduff when he murders his family.  Why?  He is
afraid that Macduff will be the agent of his fall from
power.

So, Macbeth is the main betrayer in the play, and
his motivation is the gaining and maintaining of power.