Italian and German unification in some ways mirror one another.
In the Italian context, I would say there were really two dominant personalities; Camillo Benso, Count of Cavour, in the north, and Giuseppe Garibalidi in the south. If you were to consider what "Italy" was when these two men appeared on the scene, you'd be considering a fragmented geopolitical situation: Northern Italy was divided between various small political States, as well as territories held by Austria, whose influence extended beyond these territorial holdings; Central Italy was controlled by the Papal States; and the Kingdom of the Two Sicilies was in Southern Italy. In addition, you should be aware of the idea of nationalism among Italians, which was present long before unification was achieved.
Camillo Benso, known generally as "Cavour," was the Prime Minister of Piedmont-Sardinia, one of the many Nation-States within Italy. In 1858, he signed in agreement with France, aligning the two countries together against Austria. Defeating Austria allowed for Piedmont-Sardinia to expand dramatically in Northern Europe. Meanwhile, Guiseppe Garibaldi marched across Southern Italy, and shortly thereafter, annexed these regions into Piedmont-Sardinia. Thus, The Nation State of Italy was formally created in 1861, with the former King of Piedmont-Sardinia becoming King of Italy. The last additions were Austrian controlled Venice in 1866, and Rome, which was formally added in 1870.
The unification of Germany, on the other hand, was ultimately carried out under the domination of Prussia. Prussia had already been established among the European Great Powers by Frederick the Great, and had been vying with Austria for influence among the German States. The dominant personality within the story of German unification was Prussian Prime Minister Otto von Bismarck, who was primarily interested in expanding Prussian power and domination within the region. Through the use of warfare and diplomacy, he was able to achieve that goal and, after winning the Franco-Prussian War, the German Empire was officially created in 1871.
Citation note: when writing this response, I drew on the following historical text: John Merriman, A History of Modern Europe: From the Renaissance to the Present (Third Edition). New York: W. W. Norton, 2010. The critical chapter was Chapter 17, containing the section on Italian unification (pp. 650-660) and German unification (660-673), among other subjects.