that is what my mod is about:
http://forum.paradoxplaza.com/forum/showthread.php?539095-Upcoming-Mod-A-World-To-WinI'm sorry but if the Bolshevik revolution failed then what would be the point of a "Red Germany?" The whole point of Lenin's much anticipated Russian October Revolution was to start a chain reaction of violent revolutions across Europe. The idea was that Russia would also help spread the revolution first through Poland(in order to get to Germany to help the German comrades take power) and also to aide nearby Hungary, which was struggling to fend off a Romanian assault, which historically the Bolshevik Red Army failed to stem.
Why can't German communists succeed where their Russian counterparts fail? Both countries were ripe for revolution. Interesting things about this TL concept:
-Marx will be vindicated. He expected revolution from an urban, industrial country, not peripheries like Russia and China. This combined with the first successful revolution in his home country will make him even more central to socialism.
-From this follows: communism will be more urban and industrial in character. Expect revolutions to be more likely in other urban states and less likely in more rural states. England and France will fear even more than OTL. Marxism will be just as powerful as an anticolonial ideology, especially when Germany gets in conflict with the Entente.
-Communism will have a German character. Certain issues will be linked, especially Anschluss with Austria, which the communists will likely support (Austria's social democratic party supported Anschluss before Hitler took power). As OTL, Germany may give up certain land claims for Realpolitik reasons, but push others. Italy being fascist, a Communist Greater Germany will want South Tyrol, but may not care about the Sudetenland if they have a good relationship with Czechslovakia, for example.
-Related: expect a major cleavage between workers-of-the-world communists and German nationalist communists. The latter will have some characteristics of OTL Nazis, though the unreformed right wing will be virulently anti-communist.
-Fascism may be more common west of Germany. It will be thought that the lesson Germany taught is that a democratic republic cannot stave off the Red tide. Expect fascism in France. Antisemitism will be more common in the rest of the world as well, because many of the German communists will be Jews.
-The Great Depression is, as History_Pintobean says, coming along as OTL. How the communists react will determine their legitimacy.
Something I have often thought about is what flag a Sparticist Germany would have. I hope not the OTL Soviet flag, but it is perhaps possible. They would, might retain the 1848 colors, but probably would not keep the basic tricolor. The Red Flag will continue to be used, but not as the national flag. I would expect a 2:1 red flag with a yellow and black symbol or symbols in the center or the canton. Options would include a hammer, a sickle, a compass, wheat (both as in OTL East Germany's flag), a gear, a fist, a scythe, stars, a weapon, and goodness knows what else. Heck, it could even be that two-headed eagle with a hammer in one hand and a sickle in the other, though I don't imagine they'd co-opt monarchist symbols.