Russia and China snuggling up together
This has been happening already, and this might not be such a formidable threat after all.
The West should simply take all their industrial production back from China (gradually, of course) and stop giving them access to high-tech inventions. Isolate them and eventually China will take over Russia - compare the population potential in the Russian far east for example. Siberia is already Chinese, it's only a question of time. In such scenario Russia will become a Chinese vassal and cheap ore/oil supplier.
Of course, such scenarios are rather unlikely.
My scenario is:
Russia keeps suffering high losses in Ukraine, so the unrest in Moscow grows. China, afraid to lose western money and industry stays away from the direct involvment in the conflict. Sanctions take toll on Russian economy: people are unhappy, oligarchs are unhappy and, eventually, the army starts murmuring too. In the end Putin is overthrown, democratic government takes power, political prisoners are released and Russia starts a slow (VERY slow) process of rebuilding her image as a civilised country.
Remember where you first heard it.
