Well, it's a little cliché, but let's say the Germans win the battles of Moscow and Leningrad, and Fall Blau succeeds. So, the USSR suffers badly from the loss of Caucasus (Germans might not actually invade Caucasus but will still cut it from Russia and bomb it), Ukraine as well as Moscow and Leningrad. Plus the actual defeats (for example, losses during Fall Blau, Moscow and Leningrad).
In 1944, the Red Army still manages to win, thanks to trans-Ural industry as well as lend-lease (which has to be much higher than OTL). However, the Heer practices scorched earth of its own, leaving western Russia, Caucasus, Ukraine, Belarus and Poland throughly wrecked, in terms of population, industry, infrastructure and agriculture.
Then, as the Red Army rolls in, Soviet food priorities are
1 ) Feeding Russian soldiers and industrial workers well
2 ) Keeping Russian displaced refugees (whose farms and fields were often wrecked) fed
3 ) If possible, feed non-Russian Soviets to some extent (if Ukrainian population is reduced, Stalin will find it convenient, but not too much)
4 ) Everyone else.
After the war, priorities remain the same : having large agricultural exports to get money (and buy industrial tools), feed Russian good workers, "reduce" restive nations and ethnic groups.
So, in 1944-54, every single factory of Eastern Europe is transported to Russia. Industrial workers are deported too. Food is confiscated, so famine hits Poland, Baltics, Belarus, Ukraine, Romania and Hungary for a decade.
Mass population displacements happen, mostly local workers deported to work in Russian factories or to build canals, railways, roads... As well as Russian peasants getting all the best land available.
There are also non-Russian colonists. For example, "good" Romanians would get a priviledged life... in Poland, while "good" Poles would become priviledged colonists in Hungary, and so on.
At the same time, every country develop atheist and communist elites, as well as militia forces who are loyal because they get priviledges (and often are more brutal to their own people than Russians). Local religions are heavily repressed, too.
When the Soviet Union collapse, all non-Russian countries (whether WP members or former republics) are ruined, and have Russian minorities as well as colonists from neighboring countries who are hated by locals, plus corrupt or fanatically communist native bureaucracy and militia.
So, you might get Yugoslavia-style total wars with genocide everywhere. Between Poland and Lithuania, Poland and Slovakia, Czechia and Slovakia, Hungary and Romania, Hungary and Yugoslavia, Yugoslavia and Albania, Yugoslavia and Romania, various Yugoslavian ethnicities, in Moldova, between western and eastern Ukrainians, etc. All those ethnicities and countries being competing for meagre resources.
You might also get Al-Qaeda style terrorist Christian organizations, initially anti-Soviet and then just targeting everyone of a different religion or disagreeing with them. And hardcore theocracies, for example in Poland.