I see three ways for this war to end. One, Ukraine will exhaust its forces and supply of weapons, but will not defeat Putin. At that point, it will concede the loss of some or all of its territory.
Two, Putin will exhaust his conventional forces, but will not concede defeat. He will use his tactical nuclear weapons. To avert all out nuclear war, Ukraine, and the West, will concede defeat.
Three, Putin uses his tactical nuclear weapons and all-out nuclear war unfolds.
I’m betting on option two. But if that’s the way this plays out, we have a lot of thinking to do. We cannot simply concede whatever demands Putin puts forth in the future, or can we? Having invented these horrid weapons, must we now give up all that we believe in to prevent their use? We’ve been creeping toward this fork in the road even since Hiroshima and Nagasaki. IMHO.
Grace
Sauk City Blog 
Your options are all very dark for humanity and the concept of right overcoming might. There are other options for democracy, life and justice some but not all mentioned below
1.) The Russian army puts down its weapons against its Slavic brothers.
2.) Putin dies of natural causes or is assassinated.
3.) There is regime change in Russia and Putin is held to account for war crimes along with those that supported said crimes.
4.) An ongoing war with much bloodshed and TV coverage that has no winner and exhaustes Russian resources.
5.) Russia does not use its nuclear arsenal.
6.) NATO escalates its commitment to Ukraine and a conventional war is undertaken which Putin loses.
7.) Any other combination of possibilities 1-6.
These are just a selection of what could happen. No one knows what will happen yet, but I hope we still exist when this madness has ended and that includes Ukraine and its people and their home land too.
To assume Putin must win or has already won is short sighted and I pray and hope he will not.
Greetings Huw, Theoretically, there are ways for this war to end in ways other than the obliteration of Ukraine or with the use of nuclear weapons. I absolutely hope the sanctions work to move Putin off his current trajectory. I am less hopeful than you, but I’d be happy to be wrong in my pessimism. Thanks for commenting.