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?

The vast majority of antifascist partisans in Nazi-occupied countries were socialists. We actually organize and fight while liberals create the conditions for movements like fascism.

For example, the partisans in what became Yugoslavia took back their country through their militant organizing.

Though we should not forget the antifascist force that defeated the Nazis and gave those partisans more room to operate: The Soviet Union. While Western liberal powers were sitting back hoping for the Nazis to take out Eastern Eurooe, the USSR was rapidly developing its infrastructure and productive capacity so that could fight an existential war against the fascists.

And what about the cases of socialist fascism?

That isn't a thing. Those words don't make sense together.

Fascism was a specific development in countries, specifically Germany and Italy, that wanted to become imperial powers as a new set of post-WWI great capitalist powers had basically carved the world up into pieces for themselves to plunder and had left out both. The fascists built on the prevailing conditions in those countries.

German and Italian liberals could only offer the same degrading conditions available to imperialized countries. Instead of being the vampires getting fat off the blood of others, they were trying to navigate the country as a blood-bags.

Socialists understood this and organized against it, but this, of course, threatened capital. Socialists would organize and take over exploitative factories, neighborhoods, municipalities, and run them for and by workers. Capitalists promoted the opponents of socialists, and fascists emerged as this opposition. They began as violent gangs of nationalist thugs supported by capitalists to "protect businesses" and go after socialists. Liberals supported these fascists. So did social democrars once they gained electoral power. All of the mealy-mouthed reformers empowered fascists materially against socialists.

And that is how fascists developed, in a time of crisis for how to resolve the competing forces of imperialized liberalism and socialist organization. Their angle was to develop a hyper-nationalist program against the socialist one and (on paper) against the liberal one, to explain why the common person's (Volk) conditions were degrading without actually materially addressing the capitalist system as it actually was, but through mythologies about scapegoated minorities, betrayal, and not doing capitalism well enough or for the interests of the people. Where they did have a material analysis it was in their expansionism, they understood how the imperialist equation looked, but instead of trying to destroy imperialism they just wanted to sit at its head.

And at every step of the way, socialists fought them. They were, and are, complete enemies.

Is the only remedy a more socialist organization?

There is no liberation without organization. And organization will not produce the outcomes we need without having a correct understanding and analysis of oppression and how to combat it. Therefore, we need socialist organizing.

This does not mean it is easy.