How is lady macbeth most responsible for the terrible events that happen in the play macbeth?
She has the determination to fulfil her husband's ambitions which he lacks.
Even when the witches greet Macbeth with their prophecies, he baulks, to Banquo's surprise, because they echo the thoughts Macbeth already has.
However when Duncan arrives at Macbeth's castle, he cannot at first bring himself to murder his King. Only after the pleading and encouragement from Lady Macbeth does he murder Duncan.
It is she who goes back in to Duncan's chamber to implicate his guards as his murderers. However as the play progresses, Lady Macbeth's sense of purpose and direction disintegrates as she loses her mind through guilt. It is Macbeth who continues the killing. However as the question suggests, it is Lady Macbeth who starts the process which leads to its inevitable conclusion.