For All Time did a good job with this:
-Enlarged East Germany
-Nuremburg, Leipzig and Berlin have suffered Nuclear Attack
-There is no real attempt to weed out Nazis from the country.
-SS/Wehrmacht civil war over the attempt to Kill Hitler
-Gas weapons used against Germany.
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Topping this is hard, but what comes to mind:
-Failed D-Day in 1943 means that the Western Allies don't really get into Europe. (They get France and the Low Countries)
-Hitler dies of a drug overdose, Himmler takes over in 1944. He decides to use chemical weapons against the UK and the Soviets. The UK retaliates with Anthrax, leaving the Ruhr and Berlin as uninhabitable post-war.
-Because the Allies don't really get into Europe quickly, the Red Army advances to the Rhine in 1946. Stalin doesn't even want a unified Communist Germany, so he's going to do more than adjust its geography, he's going to Balkanize the state and apply NKVD terror until it sticks.
-In OTL, little effort was made to stop Soviet atrocities against the Germans until something like two years after the war ends. With no West Germany to worry about, these orders are never really given, and the Soviets continue to pillage, rape, and seek revenge across Germany for a decade.
-Stalin, of course, is reasonably cool with nations adjusting their borders at Germany's expense. The Dutch plan to annex territory is gracefully accepted, as is giving France the Saarland.
Germany is then busted up into sixteen little pieces, all of them competing for how enthusiastically loyal they are to Communist Liberation. Post Stalin Secretaries are willing to allow a bit more freedom inside the Warsaw Pact for most of its nations, but not the Germans. They deserve what they got.