Ukraine doesn't need to "defeat Russia". Russia will, again, fail all by itself.
Putin's hubris exposed Russia's military as the corrupt, relatively ineffective in real combat with a motivated opponent with orders of magnitude less military and economic mass. Ukrainian people would rather die than live under Russian oppression and as a Russian society. Funny thing is that AFAIK, NOBODY admires or wishes to live the Russki Mir. Except ignorant Russians who are too bone-headed and have laughably false confidence in their overall superiority.
Russia is a fucked up country and Russian society is to blame. I confess that I used to have sympathy for Russian people who 'had no choice' but to send their men off to this wasteful and destructive war. Guys like YOU, A2sx, oily, that Battle Babushka with the massage parlour on Bloor as well as what I read and watch on YouTube when Russians are interviewed etc... have rekindled my, and likely most of the world's disgust with Russia and Russians.
Putin's continued obstinant pig-headedness continues to neuter Russia in incalculable ways.
Mark my words, again, Russia will fail. They already failed on every single one of their claimed reasons for invading. They are failing to win much more than when they invaded last time. Russia is failing not only in this mal-adventure but as a country. Just like they did when they poured all their money into the Cold War.
Ukraine doesn't have to defeat Russia. Russia is already doing it themselves.