If we're talking about civilians of Allied nations who believed they were being lied to about WW2 there were the kachigumi or "victory group" of Japanese Brazilians which was essentially a widespread conspiracy theory movement claiming things like Japan had destroyed the American fleet in a climatic 1945 battle thus winning the war. Several kachigumi terrorist organizations existed in post-war Brazil and were responsible for the murder and injury of many Japanese Brazilians who refused to believe rumors of a great Japanese victory.
A quick background, Brazil has had a large Japanese population that arrived in several waves during the early 20th century and today still contains the largest ethnic Japanese population outside of Japan. However, in the late 30's Brazilian nationalists began pushing for the removal of anything deemed "un-Brazilian" from public life. This ultimately resulted in bans on the sole use of non-Portuguese languages like Japanese in newspapers or radio broadcasts. That was a problem for the Japanese community because most did not read or understand Portuguese. Restrictions got even worse in 1942 when Brazil joined the Allies, culminating in the severe reduction of regular news source access for most Japanese Brazilians.
Now it's important to note that while many abuses were committed against Japanese Brazilians during WW2, internment was not as widespread as in the United States due to the unlikelihood of a Japanese attack on Brazilian soil. This left a large Japanese Brazilian population who didn't read Brazilian newspapers but were still able to communicate with one another orally or through clandestine publications and hidden short-wave radios. Many of these radio broadcasts supplied information that originated from Imperial Japanese sources and depicted a war that was going favorably for Japan.
So it caused a lot of confusion amongst Japanese Brazilians when on August 14 1945, the emperor's voice broadcast, gyokuon housou, was released to announce that Japan had surrendered. There are reports of this news being dismissed as Allied propaganda, misinterpreted, or even twisted by gossip until it became an announcement of a complete Japanese victory. Such misinformation saw significant pushback from the minority of Japanese Brazilians who could speak/read Portuguese and tended to be better educated and connected to the international world. This resulted in anger and derision from the segment of Japanese Brazilian society that was unable to accept the idea of a Japanese defeat and referred to themselves as "kachigumi" (victory party) and "shinnenha" (believers). There were many flavors of kachigumi and it was a phenomenon that also occurred in places outside Brazil. But a major theme amongst kachigumi was the belief that ethnic Japanese who refused to believe in Japan's great victory, derogatively called "makegumi" (the defeated) but referred to as "ninshikiha" (the recognition group) by themselves, couldn't be tolerated and should be targeted for violence.
Things got pretty ugly during the late 1940's. There were riots and assassinations by kachigumi groups against members of the ninshikiha, especially in São Paulo State. General anti-Japanese sentiment grew amongst other Brazilians and a ban on the arrival of new Japanese immigrants was considered. There was also widespread fear amongst ninshikiha who would sometimes receive letters from kachigumi terrorist groups demanding they perform seppuku (suicide) or face murder by firearm or katana. Finally in 1947 the leaders of the largest terrorist group, Shindo Renmei, were arrested and campaigns for outreach to Japan itself began which started the process of reconciliation and integration into general Brazilian society. Overall it was a traumatic time in Japanese Brazilian society that has a lot of complexity and nuance that I didn't get to. I'd highly recommend reading more about the subject.
Edit - Cleanup
Sources:
Japanese Emigration to Brazil. Chapter 6: Kachigumi and Makegumi