1: The various leftist resistance groups in occupied territories

2: The Catalonian anarchists and Spanish Republic after the liberals abandoned it.

3: The Maoists after the alliance with the KMT broke down

Since you "forgot."

And that's just the WW2 era. Afterwards, there was nearly a century of rat fucking "liberals" supporting fascists in South America, Vietnam, and Korea, while socialists fought them.

But, hey at least one of those kind of worked out, right?