Memes

Of course, obligatory Foundations of Leninism by Stalin, 6th chapter in particular is possibly the most concise and to the point explanation of imerialist and antiimperialist tenedencies (Stalin even calls it "objectively revoutionary" and "objectively reactionary").

Lenin writings iirc in 1919 include some letters to the emir, and also of interest might be much earlier Lenin articles about Russo-Japanese war in 1905 in which he clearly formulate theory of revolutionary defeatism and also straight up critically support imperialist Japan since at the point even clearly imperialist Japan is more progressive than half-feudal Russia and Russia's defeat can lead to changes in it (as we know it did, loss in that war was one of the main catalyst of 1905 revolution).

Plus of course Lenin's "Imperialism..."

in any case, i still think that it’s useful to make a distinction between entities that seem to be anti-imperialist as a fundamental goal (eg china imo) and clearly opportunistic “antiimperalists” (russia)

Absolutely, nobody even suggest we extend it to the past and possible future reactionary actions. In fact, Putin was heavily criticized by Russian, Ukrainian and Donbass communists for his procrastination and unwillingness to help DPR and LPR and constant reaching to the west. If west wasn't so determined to recolonize Russia today's world would look very different.