Stalin is assassinated right after Lenin dies.

[All Along The Watchtower]

What happens next? Will someone similar rise within the Communist Party leadership? Or is Uncle Joe in a class of his own?

[True Federalist (진정한 연방 주의자)]

A lot depends upon who the assassin was and how public the assassination was.

[Independents for Nihilism]

Say Здравствуйте to the permanent revolution, boys.

[PSOL]

Trotsky would be in Berlin by 1939

[The Mikado]

Oh, sure, no one posts on MY Soviet what if, but this one is blowing up.
( https://talkelections.org/FORUM/index.php?topic=452000.0 )

Anyway, I very much doubt Trotsky takes over in this scenario. Zinoviev and Kamenev still despise him (truly amazing how Stalin managed to get them executed as part of the "Trotskyite" "Left Opposition") and Trotsky wasn't close to Bukharin either. Lenin's Testament also said that Trotsky shouldn't lead (yes, it also said Stalin shouldn't lead, but Trotsky's only path to power is through Lenin's legacy because no one alive in 1924 in the Politburo wanted him in power).

[All Along The Watchtower]

Oh, sure, no one posts on MY Soviet what if, but this one is blowing up.
( https://talkelections.org/FORUM/index.php?topic=452000.0 )

Whoops, sorry.

[Agonized-Statism]

Probably collective leadership for a while. Trotsky didn't have the support, and he couldn't exactly maneuver quietly toward seizing power since everyone expected him to be the Napoleon of the Russian Revolution- Lenin included, at least that's what I got from his Testament. He would remain influential for a time, though.

The rapid industrialization and collectivization of Stalin became inevitable when the Revolutions of 1917-1923 ended the way they did, with the USSR contained and in danger of being starved out by the capitalist powers. Remove Stalin and the Soviet state still hunkers down and builds itself up at latest once belligerent anti-communist fascism becomes a wave during the Great Depression. Even if a Stalinless Comintern encourages a united front with the social democrats in Germany as Trotsky wanted, stopping the Nazis' rise to power, some kind of right-wing Germany- maybe one better at making friends than Hitler's- was likely to come out of Weimar's turmoil and push for an anti-communist crusade.

With all that in mind, someone else would emerge by the 1930s to ban factions, collectivize, and industrialize. Exactly how this process goes has a huge impact on the Soviet Union's performance in World War II.

[FT-02 Senator A.F.E. 🇵🇸🤝🇺🇸🤝🇺🇦]

Surely Bukharin would play a significant role in the aftermath of such an event.

[NewYorkExpress]

Well, most of the genocides Stalin is responsible for don't happen, and I don't think the leadership in 1939, if it isn't Stalin would sign a non-aggression pact with Nazi Germany.

[Lincoln Republican]

Vyacheslav Molotov would have made a play for power.

[Senator-elect Spark]

Trotsky rules Russia.

[Samof94]

Beria?

[The Mikado]

Trotsky rules Russia.

No way Zinoviev and Kamenev and Bukharin yield for Trotsky. There was a solid anti-Trotsky majority on the Politburo and no Stalin doesn't change that.