Putin has been back into a corner. He is losing in Ukraine, and if he should lose he will lose power in Russia and probably be killed and his legacy forever destroyed in Russia. He would kill everyone on the planet before he let that happen.
So his options now are:
-Win the conventional war. He is focusing on this option with his call up of 1/3 of a million troops. The problem here is that his troops are profoundly unmotivated whereas Ukraine’s are motivated to the max by the torture and genocide that’s happened there to their family and friends.
-Use the threat of nuking Ukraine’s army to force Zelensky into a peace treaty that lets Putin save face: this means Putin keeps 3+ territories and Crimes… Unlikely.
-Actually using tactical nukes to force Ukraine into a peace treaty. Risky, as the West could respond with overwhelming force.
-Release a bioweapon that combines the spread of COVID with the kill rate of Ebola. Wipe out half of Earth’s population than be the hero to first discover a vaccine. The war would likely end with a major deadly disease outbreak.