I did a cliche WW3 one, I had two endings. In the first one the NATO bloc wins because India nukes China after they get invaded, taking them out of the war. The AngloAmericans and Russians agree to not use nukes but without China's help Russia runs out of funds fast and they get pushed back to their current borders after an succesful invasion of Eastern Europe. I don't know how nuclear winter works but both nuked countries will lose hundreds of million of people and their civilizations might be partially destroyed, at this point North Korea could also attack South Korea and take over after nuking some city far from the border (to avoid nuclear consequences) like Daegu or Busan. This is not the only way for the US to win it's just what I thought about

In the other one, the Eastern powers win by giving Pakistan support to invade India, while China invades through Myanmar, India falls since it's fighting a two front war, Pakistan annexes any strategic territory and border regions with muslims living in them, while China breaks India up among ethnic lines. Russia takes over Europe all the way to Northern France with help from Chinese troops after the Asian theater is pretty much over. The US remains powerful in the Western hemisphere and Oceania but Eurasia and Africa will be controlled by China and Russia