What are the most extreme pro-Kriegsmarine claims you have read?
Short answer
Unsupported claims of national superiority are a recurring problem, especially when otherwise well-researched books make unchecked comparisons with other navies.
Notes
Claims that one navy could do something another could not often repeat a received national reputation. The problem can occur in a book that researches its main subject carefully but treats another service through a passing, untested comparison. British and American capabilities both supply examples of how such claims can mislead readers. These unsupported comparisons attract stronger criticism here than openly partisan enthusiasm for a particular navy.