How is Macbeth ruined by ambition?3 causes

Macbeth's tragic flaw is that of vaulting ambition.  When
the play first opens, he is a valiant and loyal soldier for the king.  However, during
his first encounter with the witches, a seed of greed and ambition is planted. At first
Banquo and Macbeth tease one another about how ridiculous the predictions made by the
witches were.  Banquo also admitted that such an evil source could never be trusted to
tell the truth.  Nevertheless, this is when Macbeth writes to his wife about his
encounter with the witches, and this is where is ambition truly rises.  It is also true
to say, that without Lady Macbeth, Macbeth probably would have remained a true and noble
soldier to the king.  But, upon reading her husband's letter, she immediately becomes
obsessed with the realization of the prophecies told by the witches.  It is this very
ambition which causes Macbeth to kill Duncan, to kill Banquo, for Lady Macbeth to have
killed herself because of overwhelming grief, and which brings Macbeth to his own
untimely death.