After that, Russia is out of any international organization, relations and society. It will be second North Korea.
I wouldn't risk nuking Ukraine, they have shown exceptional resilience and ingenuity. Russians Invaded their country, slaughtered their people raped their women, then you drop a nuke on them because your losing a war you instigated. Ukrainian intelligence after such an incident would probably obtain their own, hide it in a lorry somehow and then place it right next to Putin's residence.