Well, the recent celebrations of the 60 year anniversary of the end of the Second World War, where France, Imperial Germany, the United Kingdom, Japan, and the United States defeated the greatest threat to peace ever imagined: Trotsky's Soviet Union. Now, it seems kind of implausible, but what if Joseph Stalin, who Trotsky had killed, became premier instead? He had an approach of building relations with non Communist countries. Could a Stalinist Russia actually survive as a Communist nation? Could we avoid a Second World War under Stalin? I don't see any other dangerous ideology catching on.
Well, firstly, perhaps the Cold War would have been with Russia, instead of a hyper-powered Nationalist China.....
Also, to get an idea of what Stalin actually would have been like, I'd like you to read Harry Turtledove's excellent "The Red Tsar" from 1991(the year that the Sino-American detente finally ended and China collapsed) at some point.....Stalin was *not* the great pragmatist that he was made out to be; sadly, in fact, he would have been far, far worse for Russia than Trotsky ever could have hoped to be; Trotsky, in fact, was rather restrained, until Stalin tried to have him assassinated, and only after that, did he start becoming paranoid.....and even then, Trotsky's government wasn't terribly bad towards the common people(although, granted, Trotsky was fairly ruthless towards "enemies of the State", including the conservatives of the Russian Orthodox Church).
In fact, if you want worse, go look at Imperial Germany's treatment of the Roma during the Emergency Government during the last nine years before it collapsed in 1989(there's a reason why Kaiser Wilhelm V was tried for crimes against humanity.....and was almost universally disliked by even many German conservatives-he ended up signing the legislation that took Germany's constitution and pissed it all away.); it might not have been a full-blown genocide, but it was still damned awful nonetheless.
OOC: Sorry to break this to you, OP, but I'm afraid that this whole scenario might well require a rather different Stalin and Trotsky to really work, especially the later the POD.