[dude with glasses in a communist t-shirt, arguing] I'm the only leftist here, your opinions are TRASH
[dude holding a theory book on smug, arguing] Read theory you losers, you're all WRONG
[dude in an anarchist hoodie, arguing] Nuh-uh, I'm the only leftist here, you're SHITLIBS
[the three dudes are now caught in a cartoon fight, glasses gone flying, punches everywhere, while a firing squad of nazis are targeting them with rifles]
[a confused nazi asks] Why… why are they still arguing?
Not really sure what you're trying to say here as "Marxism and Marxism-Leninism." Are you saying these are antagonistic ideologies? Marxism is an umbrella, not a tendency within itself. History has progressed since Marx, and Marxist theorists since Marx have developed theory and practice accordingly. By far the largest tendency in Marxism is Marxism-Leninism, the closest to a "pure" Marxism you can get is Orthodox Marxism, which itself is ironically anti-Marxist and is overall an extreme fringe belief among Marxists.