Can Ukraine win on their own?
No. Russia has at least 3X the military potential of Ukraine. Thats why Ukraine has supporters, because everyone else on the continent is, individually, inferior to Russia. They must stand together or fall separately.
Its the same for any smaller state with a bigger neighbor.
How many small countries can win a conventional war against larger invading nations without outside aid? The only other option would be a bloody 10 to 20 year insurgency. Is that what you wish for?
Can Russia win on its own? Obviously, not. They import weapons from Third World Countries and exports keep their petro economy from cratering.
There is really nothing to negotiate until Putin accepts that Ukraine is not part of Russia and therefore Russia has no business setting Ukrainian policy. Russia will have to be making security guarantees to its neighbors to assure it does not invade any more of them.