Your seemingly innocuous question contains a poison pill - i.e., a false premise.
Without Western intervention (military and humanitarian aid), the Ukrainians and the Russians would namely not "decimate" each other.
Rather, Russia would simply conquer Ukraine, which would then be partitioned, dismembered, depopulated, Russified, and eventually converted into a puppet regime with a tin-pot dictator like Lukoschenko, wholly subservient to Moscow, heading it - comparable to the way Belarus is now merely an appendage of Putin's resurgent "Greater Russia."
Like in Belarus, Putin would then move in his nukes and his troops - in preparation for attacking his next target.
Your proposal - to let Ukraine and Putin's Russia simply "duke it out" - is as ludicrous as suggesting that Dick Cavett should go 10 rounds with Cassius Clay (in his prime) and in this way "settle their differences."
Regards,
Well, it is not up to us who controls Ukraine.
It is their fight regardless who comes out on top.
It was the rest of Europe who wanted this, and got the Democrats on board.
This is a question that really will not lead to a resolution, since we do have half the politicians in this country who care more about what the rest of the world wants.
My answer still stands, what country has not backstabbed us.
I can accept South Korea, and may Vietnam, but only because they defeated the side we fought for.
Well even then American Democrats defeated us not the Viet Congress.