The rise of fascism in Italy was primarily influenced by factors such as economic instability, nationalistic sentiments, and dissatisfaction with the outcomes of World War I, particularly stemming from the Treaty of Versailles. Therefore, among the options provided, the Treaty of Versailles is the most relevant factor in the rise of fascism in Italy.
The other options listed, such as the German-Soviet Nonaggression Pact, the Treaty of Berlin, and the Munich Pact, are more related to events and agreements that occurred later or pertained directly to Germany and its foreign relations rather than Italy's internal political evolution leading to fascism.