Lenin was an intellectual from a very good, noble family who had a traumatic experience shortly before leaving school: his older brother was executed for revolutionary activities. Lenin then decided to join forces against the tsar's family and complete his brother's work. This did not go unnoticed, and Lenin was forced to go into Western European exile.
Although Lenin was primarily a theoretician, he was extremely popular among the Russian Bolsheviks and was accepted by them as a leader. When the Germans were at war with the Russians in World War I, they had the brilliant idea of enabling Lenin to return to Russia so that he could start the Bolshevik Revolution there. The rest is known: The revolution was victorious, Lenin became Russia's new head of government, and Russia made peace with the German Reich.
Already a few years after the revolution Lenin fell seriously ill; his death was already foreseeable. Among his comrades-in-arms there were, as expected, outbreaks of fighting for his successor. After all, Lenin was decent and clever enough to warn against Stalin because he had recognized his sociopathic character. Unfortunately, this warning was of no use.
In contrast to Marx, Lenin was not a pure busybody, but acted out of a personal motif. In addition, he stood much more firmly in life. His warning against Stalin is positive. Nevertheless, I don't want to give him an absolution.
As far as his theoretical achievement is concerned, he distinguished himself primarily as a recipient of Marx's teaching. But he also developed it further by, among other things, thinking about the structure and organization of the Communist Party (and putting it into practice).
Claus Volko, MD MSc