What are the opposition forces for the witches?

THere was always the outside chance that Macbeth will find God again and rebuke the witches. I think the witches knew they were pretty safe though.

The biggest opposition the witches face is Macbath himself. Before the witches, Macbeth is an honorable, loyal warrior. Their influence shifts his obligation, but his conscience works in complete oppostion to what they want to accomplish. In the end, Macbeth does what they forsee, but it also destroys him because he cannot live with the guilt.