*rolls eyes at everyone answering "he'd die"* GEE, YOU THINK?
Agreed. TERRIBLE decision on those soldiers part. I would expect the fear of such repercussions would be enough to keep him alive. Alive enough, anyway. Stalin wouldn't mind some broken ribs.....or a missing finger.....castration might fall into "denying Stalin his prize" territory though. Not too many blows to the face, comrade. A little game of Whisper Down The Lane develops where each unit gets a few careful but very satisfying licks in before transferring him.
I absolutely believe he gets put in the finest bulletproof glass cage Soviet engineers can produce (with enough gaps to allow oxygen and non-lethal vegetable projectiles inside) to become part of the Moscow Victory Parade though. Try to imagine Cersei's Walk of Shame, but if she had murdered a family member of everyone in King's Landing. Phew.
After that epic catharsis, who cares what happens to him, right? Would definitely be rumors of Soviet super-science keeping him alive for torture to the present day tho lol.
The gulag will do just fine to make him suffer, though, with his medical conditions, he'd probably expire quite fast in the Russian wilderness.
As for the reaction from the West, I'd imagine a few urging Stalin to prosecute him at Nuremberg and give him a fair(er) trial, but they probably won't complain much if he gets sent to a show trial in Moscow anyway. In fact, there's more than enough damning evidence against him it'll be a sick joke to actually falsify any (though exaggerations of his crimes are expected).