Right now, Ukraine.

So much Russian oil infrastructure has been blown up that Russia is negotiating with Kazakhstan to import gasoline to alleviate shortages in Moscow: https://english.nv.ua/business/moscow-arranges-gasoline-imports-from-kazakhstan-50619044.html

In Crimea, gas and diesel sales to non-governmental entities have been suspended entirely: https://english.nv.ua/russian-war/fuel-sales-halted-in-occupied-crimea-as-fire-burns-at-kerch-fuel-terminal-50617995.html

This doesn't mean Russia is going to collapse right away – I wouldn't be surprised if we have another two years of war – but it does mean there is a feasible path to total victory for Ukraine. All they have to do is hold on, while destroying Russia's economy. Eventually the front lines will simply collapse due to lack of fuel, ammo, and food.