Oh I'm sure many will meet an unpleasant fate, I wouldn't expect a captured sniper to last long if they were sniping women and kids. An over run artillery unit destroying a city might suffer too, so would any of these viscous foreign fighters from Chechenia. Young conscripts would be disarmed and released, regular professional combat troops would be detained. However because there was no declaration of war or other UN approval, all the Russian soldiers in Ukraine are criminals and can be imprisoned as such, not prisoners of war. Captured generals will be shipped off to The Hague for embarrassing public trials for crimes against humanity!