I would start with a general statement about the play. Then rephrase the essay question in one or two sentences. Then establish the thesis.
Here is some help on the thesis:
Keep in mind that the fact he will always protect his crown is foreshadowed in his violence committed against Duncan. And foreshadowing is sometimes used to foreshadow his downfall. So include points similar to these in the these. Just state your opinion about the question without using "I"
