Rasputin is nowhere near the greatest Russians, in fact he pretty much sealed the deal for the commies to take power with his bullshit. I think its got to go for either Catherine or old Uncle Joe.
Catherine the great pretty much expanded Russian influence beyond anyone before and maybe since, as well as elevating their culture to bring them into the modern world at the time of her reign. If her successors had followed her example, Russia would still hold Alaska and probably wield way more political influence in the west, rather than rely on raw power and zerg tactics. Russia was pretty much the equivalent of a Middle Eastern shithole country before she came along.
Stalin was an evil bastard and murdered so many Jews that it would have made Hitler blush. But he was also the right dictator and tyrant at a time when Russia needed one, pretty much holding the Soviet state together through shear force of will during WW2 and making that beat to shit commie war torn shit hole into a viable rival to the US in a very short time. He bent both FDR and Churchill over at the Yalta negotiations, despite having very little leverage. And he managed to make commie practices almost work for a while. Dude was ruthless and single minded, wielding raw power in ways not seen since the ancient days of Greece. And if it were not for Mao he would be the GOAT in numbers of his own people killed off. But monster or not, Russia ended up going from almost being completely turbo fucked by the Axis to the boogeyman of the entire work in the span of a little more than a decade.