I just don't see this ending well. Other than a direct war, which seems bound to happen anyway some years from now unless a radical change happens to the Russian government, I don't see a way that Russia can be defeated in the short term without risking a nuclear exchange. Perhaps since conflict seems inevitable it has to be done right now, hoping that Russia's nuclear arsenal is as unprepared and incomplete as Russia's army has proven to be and that damage to the west's side will be limited. But that's one heck of a gamble to make and it'll birth a generation of young Russians who'll hate the west enough to want revenge someday.

Long term I guess the west could accept that its past failings will now cost a lot of east european nations their sovereignty, before they slowly starve Russia's economy into going bankrupt by maintaining a boycot. This'd mean that all member states of Europe need to resist the temptation of continuing gas and oil trade with Russia as soon as the war is over. Maybe they can step it up further by somehow throwing them off the Internet if that's even possible? Or convincing Russia's remaining allies that it's in their best interest to stop an ally by making lucrative offers to sway them to the other side?

Then when Russia collapses through isolation and the starving population has a revolution, the west can offer food and supplies to rebuild in return for complete nuclear disarmament. Of course it's likely that an ignored Russia will just reach for the bombs anyway when that country starts to fall apart, feeling they have nothing to lose. It's all very scary and I don't feel we can just safely assume things will blow over, Russia isn't likely to go through some kind of political change from within anytime soon.