It depends what the end of the war looks like and what happens during the peace process. I'm guessing there will be resistance/guerrilla/terrorist attacks against Russia or people/institutions perceived as Russian but those won't necessarily be big news in the west. What will make headlines will be the ideologically committed Nazis lashing out at those they perceive as having "betrayed" them. America is probably safe from this retaliation (but I won't rule out ukrainian Nazis pulling off an attack in america) so I think the most likely targets would be in Europe using some of the military weaponry that was flooded into Ukraine. I've said this before, but a large long haul airliner taking off over a major metropolitan area would be a very tempting target for a cell of Nazis with a couple stingers or similar small, man-portable anti-aircraft weapons. Or hell, maybe they'll put their drone piloting skills to use and go on a terror bombing campaign that way. The possibilities are endless for a slightly imaginative terror group sitting on a pile of military weapons