He’s worried that he’s going to get couped in a similar style to the Tsar, because all things considered, the Bolsheviks were an extremely weak fighting force compared to the Imperial army, but after their ranks were bolstered by defectors from WW1, and with the popular will of the people, they were able to sweep the Whites aside with relative ease.

So I don't know quite what to think of this, and I haven't listened to the speech yet, but according to Alexander Mercouris -- who isn't a communist by any stretch of the imagination -- Putin was referring, not to the events in October 1917, but in February of that same year. That is, he sees power plays within the Russian government as a key factor in the Tsar being "manipulated"into resigning, which of course led to the Provisional government and the Kerensky regime. This view of history may be a bit suspect, but it also isn't explicitly anti-Bolshevik (you could, under this interpretation, view the Bolsheviks as a strong force which seized control in the middle of chaos and prevented Russia from becoming a western fief).

Several different events happened in 1917. He could also be referring to the failed Kornilov coup. He could be referring to the forced abdication of the Tsar and the establishment of Kerensky's provisional government. But given that we know that he is an anti-communist and despises Lenin the likeliest option is that he means the October revolution and the subsequent signing of Brest-Litovsk which is viewed by Russian nationalists as a sort of stab in the back as they believe they were winning and that was a needless capitulation.