@Jayjay By "win," we need more clear definition.
At this point, I do not believe that anybody, even anybody with sense in the Russian government, believes that Russia is going to march confidently into Kyiv, rename it "Kiev," and install an obedient jumping jack with a rigged vote. Only a lunatic still thinks that's going to happen.
However, the government of Ukraine has not managed to take back Crimea after several years. I do not know enough about the situation in either Donetsk or Donbas to say for sure what their future is.
I am reasonably hopeful that Ukraine will be able to take back Kherson and Melipotol with adequate international support.
Hell will freeze over solid before Russia holds Mariupol. If Putin is mentally handicapped enough to think he can hold that hornet's nest, then he is more daffy than I originally thought. Mariupol's babunyas are more vicious than his most murderous general. Those people are crazy.
Whether or not Ukraine can succeed at holding all of their territory and throwing off Russia's unlawful occupation of Crimea, which I am not certain they cannot, I believe that Ukraine will ultimately come out of this situation better than Russia.
After all, Ukraine has never had more moral credibility in the international community. Furthermore, they have kindled that rare but magical political alchemy between progressive liberalism and national pride, which almost guarantees a vigorous progressive government for at least a couple of generations. Culturally, intellectually, and economically, Ukraine would still thrive even if they lost substantially more territory than they are conceivably likely to lose, at this point in the war. Furthermore, as hard as it makes me sound if I seem to treat human life as if it were fungible, which I assure you I really do not, Ukraine is nevertheless likely to have a population boom in the wake of the war, so their population is likely to be increased within a generation, rather than decreased.
Russia, on the other hand, could only get all of the sanctions against them removed and restore their image in the eyes of the world if they handed Putin over trussed-up like a chicken on a silver platter and said "Hang the bastard, for we are tired of him, now." As long as Putin remains in power in Moscow, he will be a political liability to that country. The Russian government has most likely caused irreversible damage to their international relations, and I honestly doubt they can realistically recover short of the European Enlightenment finally reaching Russia, centuries late. Furthermore, they have proved to Europe what folly it is to let themselves into a position where they need to depend upon Russian fossil fuels, and politicians in Europe that call for the further development of solar and wind energy and other efforts at achieving energy independence are likely to be profoundly popular throughout their polity: this is ultimately going to cost Russia more, in the long-run, than they could have possibly imagined. Finally, western Europe has not been this politically unified in centuries.
Even if Russia were to succeed at clinging to a few ill-gotten postage-stamps of territory, to call this a real triumph for their country would be delusional. The only way that Russia could even hold that territory would be if they gave up before Ukraine finished butchering their army. If it never occurs to them to retreat, then they will even lose Crimea. Ukraine has become a death-trap for their army, and retreating to soil that they have a chance of being able to hold is their only hope for gaining anything at all by this fool's errand.