Use 'beyond belief' to stress the intensity of something positive or exceptional.

Intensity Emphasis

It expresses a high level of surprise, often in a positive context.

Positive Surprise

It's an example of hyperbole—exaggeration to make a point rather than a literal truth.

This phrase emphasizes something extremely negative and usually unacceptable.

Use it when you want to amplify how shocking or unexpected a negative situation is.

It can strengthen criticism, indicating that the situation has crossed acceptable limits.