The factor in the rise of fascism in Italy among the options listed is primarily the Treaty of Versailles.
The Treaty of Versailles, signed in 1919 after World War I, imposed harsh penalties and territorial losses on Italy, which led to widespread discontent and a sense of humiliation. This dissatisfaction contributed to the rise of nationalist movements and figures like Benito Mussolini, who capitalized on the desire for national restoration and unity, ultimately leading to the establishment of a fascist regime.
The other options (Munich Pact, Treaty of Berlin, and German-Soviet Nonaggression Pact) are more relevant to events occurring later in the context of World War II rather than the rise of fascism in Italy, which was more significantly influenced by the post-World War I context and the Treaty of Versailles.