Huh?

They weren't in the film because the film is set in Mexico in 1940, the last year of Trotsky's exile. Lenin died in 1924, Trotsky was chucked out of the USSR in 1929. We see Stalin's assassin Ramon Mercader, but we don't see Stalin, who was back home in Russia. OK?

Incidentally, one of the user comments refers to Trotsky having been outmanoeuvred by Lenin and Stalin. He was outmanoeuvred by Stalin. Lenin's (suppressed) last testament advised the politburo to remove Stalin from power immediately but praised Trotsky as by far the most able member, if a tad arrogant. History might have been very different if his advice had been followed.

No, the characters of Lenin or Stalin are not featured in the film. The film is about the last few months of Trotsky's life when Lenin was already dead and, as his last days were spent in Mexico, we don't get to see anyone playing Stalin - although we hear several references to him and his plot to have the eponymous hero assassinated.

Lenin appears in the opening photo montage. There might be a Stalin poster or two in some of the demonstration scenes.

"The melancholy truth was that his glorious golden head had nothing in it."

datrex1, you need to review your history books. The movie is not great, but considering the title, anyone would know that Stalin nor Lenin have reason to appear in it...