Stalin eats a self-inflicted bullet when he has a mental breakdown after scurrying away to his dacha in the opening stages of Operation Barbarossa. The Soviet government plunges into confusion and infighting, as the various magnates struggle with each other to establish a new chain of command. Eventually a Red Army and CPSU-backed Troika of Molotov, Voroshilov and Zhukov stabilises a post-Stalin Soviet government, purging Beria and neutering the NKVD in the process.
The Germans make greater gains into the USSR than IOTL amidst the chaos of Stalin's suicide, but eventually the Soviets rally under the Troika and begin pushing them back. Lend-Lease from the WAllies begins flowing to the Soviets once the Troika shows its determination to continue fighting the Axis.
Since Soviet lines are pushed further back, and the Red Army is much more damaged, and the Axis has captured more Soviet territory, Anglo-American landings occur in Greece and the Balkans (in addition to the landings in France, Italy, the Low Countries and Scandinavia from IOTL). At great cost in blood and material, the Allies liberate the Balkans and most of Austria and Czechoslovakia, while the Bulgarian, Hungarian, and Romanian governments defect to them. Hungary and Romania descend into civil war pitting the German-backed fanatics of the Arrow Cross and Iron Guard parties (respectively) against the more moderate government forces, which assists the Allies in securing both countries. The Allies also occupy most of Germany once the Third Reich falls.
Meanwhile, the Soviets have only managed to liberate their own territory, while also driving into Poland, East Prussia, parts of eastern Germany proper and a small portion of eastern Romania (where they meet Allied troops, halt and don't advance any further into Romania), before the war ends. The Soviets also don't have the capability to drive the Japanese Kwantung Army out of Manchuria, and so only make a minor impact in the closing stages of the war in the Far East; (Imperial Japan still surrenders due to American atomic bombing, but the entire Korean Peninsula is occupied by the WAllies, while the Kuomintang get to reoccupy all of China - with WAllied assistance - after the war ends, leaving Mao's Communists bereft of the massive postwar Soviet support they received from the Red Army in Manchuria IOTL; instead, the Troika pursues good relations with the ROC and Korea is unified under a democratic government).
In exchange for huge Marshall Plan aid to help rebuild their destroyed country, the demilitarization of Germany, thorough de-Nazification and war crimes trials for fascists across all the former Axis nations, and demilitarised Polish and Romanian borders, the Troika agrees to withdraw from Poland (where the Polish government-in-exile returns from London and is restored to power) and the small portion of eastern Germany occupied by the Red Army. However, the Troika annexes East Prussia into the USSR and expels the German population from there, and also holds onto part of eastern Poland and eastern Romania. (The Soviets also sign their OTL peace treaty with Finland, and were incapable of joining the British in occupying Iran ITTL).
Democratic governments are established in Poland (which is smaller than its post-war size IOTL), Hungary, Romania, Czechoslovakia, Bulgaria, Albania, and Yugoslavia, while Germany is reunified under a democratic government but demilitarized (much like Japan IOTL). The Soviets have made minor territorial gains from eastern Poland and eastern Romania, in addition to annexing East Prussia.
The Cold War basically doesn't happen ITTL.