To an extent, Prussia's greatness was founded on the unprincipled conduct of Frederic II, whose theft of Silesia was inexcuseable. Prince Bismarck followed in that tradition with his 1866 war that completed the exclusion of Austria-Hungary from German affairs.
I consider Kaiser Wilhelm II the most honourable of the Hohenzollerns, on a par with Friedrich Wilhelm I. It is one of history's tricks that Prussia's destruction (or, more hopefully, abeyance) was brought about precisely because the German Kaiser did not regard his alliance with Austria-Hungary as a "scrap of paper," even when it would have been in his nation's best material (but not moral) interest to do so.
The great and Illustrious Fredirick almost lost his throne over seizing Silesia despite his efforts he had to fight on 3 fronts at once only the death of Empress Elizabeth saved him from deposition and probably the gallows.