Bismarck is the outstanding Prussian/German of the mid 19th century. It was Bismarck who saw through German Unification in 1871. He famously remarked that Unification would not be brought about 'by speeches and the resolutions of majorities but by blood and iron'. And, so it was to prove as Bismarck took Germany to war, firstly with Denmark, then with Austria, and, finally, with Napoleon III's France. Yet, Bismarck was no Hitler committed to a Europe dominated by Germany. Bismarck's aim was the consolidation of Germany under Prussian rule. He had no wish to drive eastwards towards the German lands of Austria. His dream was of Little Germany (modern day Germany) whereas Hitler's dream was of a Greater Germany (encompassing Austria and other lands where Germans were living in significant numbers - of course, his dream went even further with his attempts to crush France, Britain, and Russia). We should remember when contrasting the two men that Bismarck was a Prussian whilst Hitler was an Austrian.
The idea of German Unification, whether Little or Greater Germany, had been around since Napoleonic interventions in the political structures in Europe at the beginning of the 19th century.
Bismarck changed the history of Germany and of Europe and his legacy lives on in today's Democratic German state, and, arguably, in Germany's leading role within The EU.