Prussia's militarist tendencies are infamous. There's the old joke that they were "an army than inherited a country". Prussia famously unified Germany through "blood and iron". West Germany's first Chancellor, Konrad Adenauer, squarely blamed the Prussians for the rise of the Nazis.
The obvious solution to this is for Germany to be unified by Austria instead of Prussia. But is there any reason to believe that this would make Germany any more peaceful?