I admit I’m ignorant on the issue, and you seem to know: what are some examples of socialist organizations being the main force in stopping fascism?

WW2. Soviet Union inflicting more than 80 percent of losses + partisans in the Balkans freeing themselves. Italian partisans were also not given credit for their huge role in liberating Italy. Most resistance in fascist territory had a huge socialist contingent. Romania had a socialist movement that pulled off a coup during ww2 as the Soviets were making their push back to Berlin, saving a massive amount of lives.The socialists during the Spanish Civil War, although they were basically just Spanish Republicans + limited soviet aid fighting against half of Spain, and massive German and Italian forces, so they lost.

In Germany, the socialists fought the fascists but the liberals were more willing to form a coalition with the fascists than with the socialists.

And what about the cases of socialist fascism? Is the only remedy a more socialist organization?

Could you define what you mean by this? Because fascism is a specific thing that emerges within capitalism. There is no such thing as socialist fascism, as someone who has done a lot of learning on the history of fascism and socialism.