My favorite thing about VasiO is its one-sidedness, and how that makes it such a great potential for both comedy and tragedy.
It's very funny to me how Vasily canonically has some kind of obsessive hate-crush on Ogata, and has been presumably stalking him ever since their first duel at the Russian border. Meanwhile, Ogata completely forgets Vasily even exists up until the Sapporo Brewery arc, and when he does realize, it's just, "Oh. It's that guy again. Anyway-" Like, Ogata does not give a fuck about him as a person, only as a potential hindrance to his plans.
But that's exactly the part that makes it tragic as well. By this point in the story, Noda has drawn many explicit parallels between the two of them to show us that they're very similar characters. Combine this with Ogata’s rigorous but misguided aversion to having anything resembling a happy, healthy relationship, resulting in a deep, soul-crushing loneliness that he actively tries to deny about himself.
And then you realize that there's a world out there where the two of them could've been friends (maybe even more 😏). Because they have the greatest potential to truly understand each other more than any other characters in the story. But their very natures won't allow that level of human connection, especially with each other. And it's precisely because they're so similar. They're both too prideful in their marksman skills (because it's the one thing they consider themselves useful for), they're too socially avoidant, and too obsessed with achieving their goals.
Only difference is that Ogata’s goals have nothing to do with Vasily, but Vasily’s goals have everything to do with Ogata.
I think on some level, Vasily himself recognized that lost potential for connection and understanding. Which was why he never let Ogata go, even until the bitter end. "Death of a Wildcat" really is the final nail in the coffin in that regard. I can only imagine how lonely he was throughout his life.