Just two remarks about Prussia:
1) Process of nation building
The kings of Prussia did - a little bit late - what the kings of France (which conquered Burgund, Savoy, etc.) and England (Wales, Scotland, Ireland, and a little bit of the rest of the world ) had done some hundred years before when they established their respective nations / unions. They all eat their neighbours in order to establish a strong central state and a nation. Due to historic reasons this happend in Germany as late as in the 19th century, but it was a necessary process implicated for example by economic (Zollverein) and cultural reasons. The German peculiarity was the Austro-Prussian dualism, won by Bismarck, which led to a Prussia dominated small Germany ("Kleindeutsche Lösung").
2) "Aggressiveness" of Prussia
Compared with the above mentioned states UK / England and France, Prussia was a quite peaceful state in the 18th and 19th centuries. I take some figures from Berndt: Die Zahl im Kriege, Vienna, 1897 (available in Google books, tables 1-7): In the 19th century,
+ Prussia had: 12 war years
+ France: 27 war years
+ England: 21 war years
(+ Austria: 17 war years
+ Russia: 24 war years)
Regarding "Europe's long-term benefit" (somewhat off-topic here, I know), I guess that you allude / insinuate (? anspielen) on WW I. From my point of view, Prussia / Germany was not the single aggressor in 1914 - cf. the latest book of Christopher Clarke - rather there were 5 major powers in Europe (France / Russia / UK as the "entente" and Germany / Austria as the "Mittelmächte") plus an aggressive Serbia which played together a very dangerous game which went down into a hell. Of course, Prussia / Germany had its share in the disaster, but others had their shares, too...
Best regards, Thomas