I'm uninterested in that, but let me give you a limited response in two parts:
1. I consider nuking a major city a war crime, regardless of who does it (the US, Russia or Ukraine).
2. If Ukraine or Russia nuke any city there will be world trouble of the sort that will make our little conversation here irrelevant. So pray it doesn't happen.
Thankfully this scenario is highly unlikely.
If RF will kill millions of Ukrainian with conventional weapons, like they did in 1932-1934, or capture and destroy another major city, like Grozny, it's OK for you. If Ukraine will do the same for RF in return, then it's war crime for you, because victim of conventional weapon ≠ victim of nuclear weapon. Right?
> Thankfully this scenario is highly unlikely.
Two nuclear nations are at war since 2014. Where you live?
I obviously see difference, but a war crime is a war crime.
> Where you live?
A world in which neither the Ukraine nor Russia are stupid enough to risk nuclear escalation and obliteration.
Where do you?
> Where do you?
In the world where RF is stupid enough to invade the nuclear country.
I'm from Ukraine.
To be fair, the only one even considering using nuclear weapons seems to be you, here on HN. No military or political planners are considering it because nobody wants to see Europe devastated in a nuclear war, and everyone understands this, which is why -- if there is war, hopefully not! -- it won't be nuclear.
If you think about it, YOU, an Ukrainian, don't really want Ukraine to attack Russia with nukes. Why? Because then you'd be dead, plain and simple.