The elephant in the room here is what constitutes a win, and this feeds specifically to your point of what compromises would be tolerated from Ukraine.Or they could win.
I don't really like the idea of making compromises in a genocidal war of aggression but it really can't be on the table so long as Ukraine are still anywhere close to the front foot in the actual fight.
And tbh I'm not sure what compromises there are to be made down the road that actually are good long term for anyone but Russia.
Russia isn't going to surrender. Therefore, the most appropriate outcome for Ukraine would be Russia to return to the original borders, releasing Crimea.
But again, how would that come about: full de-escalation by Russia? Regime change? Promises to not be an aggressor again? Sadly, I can't see these as likely.
Or at least not a combination of all, or to a point that Ukraine and Co. will believe and feel safe. Ukraine can't sustain this type of military campaign for years.
Ukraine is never, ever going to progress into Russian territory as that would be crossing the line of a thermal nuclear response. So how does it come to an end?
We're therefore, then, potentially looking at a war of attrition, which will likely push Ukraine and Russia towards a compromise of some varying degree.
Unless we have unconditional surrender, which ain't happening, there needs to be a negotiated truce and with that comes compromise from both. But not yet.
