A man with profound, established depressive illness comes to believe, arising directly out of his overwhelming sense of worthlessness, that he has committed unforgivable sins and deserves severe punishment — a belief that developed gradually and can be clearly traced back to, and understood in light of, his underlying depressed mood. What kind of delusion is this?

This is a secondary delusion: a fixed false belief that can be traced back to, and understood as arising from, another underlying morbid experience — here, his profound depressed mood — rather than appearing as something entirely new in its own right, exactly the pattern the phenomenon's own text describes. It is not a primary delusion, which by definition arises without being understandable in light of any preceding morbid state. It is not a delusional perception specifically, since no particular normal perception is described as suddenly acquiring a delusional meaning. And it is not an overvalued idea, since this is described as a fixed, held-with-conviction belief, not merely a dominant, strongly-felt idea.