There would be no Hitler without Stalin to begin with, while the opposite isn't true.
Besides, the UK has committed acts of (de facto) shameful collaboration with Stalin, such as the forceful and brutal "repatriation" of Cossacks to the USSR where they faced certain death.
To quote Wikipedia, "On 1 June 1945 the UK placed 32,000 Cossacks (with their women and children) into trains and trucks and delivered them to the Red Army for repatriation to the Soviets [...] most Cossacks were sent to the gulags in far northern Russia and Siberia, and many died").
This was an enormous tragedy and human rights violation, comparable to what deporting thousands of North Korean refugees back to North Korea today would be.
The Cossacks knew it was a death sentence, and they resisted, but obviously in vain. In the words of Julius Epstein (after Wikipedia again): "The first to commit suicide, by hanging, was the Cossack editor Evgenij Tarruski. The second was General Silkin, who shot himself...The Cossacks refused to board the trucks. British soldiers [armed] with pistols and clubs began using their clubs, aiming at the heads of the prisoners. They first dragged the men out of the crowd, and threw them into the trucks. The men jumped out. They beat them again, and threw them onto the floor of the trucks. Again, they jumped out. The British then hit them with rifle butts until they lay unconscious, and threw them, like sacks of potatoes, in the trucks."
No British Jews have ever been deported to the Third Reich. And this certainly may add to the sense of contempt for Stalin, as the Soviet dictator sort of corrupted British politics making the UK an accomplice in a way Hitler never managed to.
> I suspect this is as or more likely a result of his [Hitler's] abundant comic depictions as it is the characterisation as a hero-like figure manfully struggling against inevitability.
That's an alternative explanation, sure (although personally I tend to doubt it)