Let's game out the "Russian whole" scenario for a minute. Let's say that Putin feels cornered, and sets off a nuke in Ukraine. What then?
One scenario (1): NATO responds by wiping out Russia's entire military operation Ukraine in about 2 days, using conventional weapons. Maybe they even go after all Russia's missile submarines. Maybe the rest of Russia's navy disappears, along with their satellites. Now Russia is fighting absolutely blind. What does Putin do here? Set off another nuke in Ukraine? That's status quo, except now, nukes are the *only* thing he has. Does he continue lobbing them willy-nilly at Ukraine? To what end? With no army to occupy the territory, it would accomplish nothing except increase his own cost of rebuilding, and further isolating him from the world.
Another scenario (2): NATO doesn't respond, but Ukraine surrenders, since it's much more likely than before that Putin will detonate another nuke. Tens of millions of people flee the country. Russia takes over, but now they have to deal with a radioactive city, a whole lot of rubble, and resources that Russia doesn't have the ability to exploit. This is the *best* scenario for Putin.
A third scenario(3): NATO doesn't respond, but Ukraine keeps fighting, and the West keeps supplying them. Will Putin drop another nuke? That just gets him back to either status quo, or scenario 2, but worse.
A fourth scenario (4): NATO responds with nukes, somewhere, and Russia uses that as an excuse for a full-on nuclear exchange.
Scenarios 1 and 4 don't help Putin establish himself as a great leader, but rather "the doofus who got our military wiped off the map" or "the doofus that started nuclear armageddon." Scenario 2, at best, labels him as "the idiot who ruined the place we wanted to conquer." If Ukraine wears down the Russians to the point they have to leave, Putin becomes "the moron who destroyed our army and economy."
IMO, the only way Putin gets in the history books for a good thing is if he is able to claim some sort of victory in Ukraine without nukes. And even then, it's likely to be at the cost of Ukraine joining the EU, and some of Russia's northern neighbors joining NATO.
Realistically, though, we are all just speculating at what Putin might do, and that's probably exactly what he wants. We've already called his bluff several times over the last few weeks, by imposing sanctions and continuing to arm the Ukrainians. If that keeps up, and the Ukrainians continue their success against the Russian army, he'll have to decide whether conquering an irradiated wasteland is worth the effort.