How were defeated nations treated by the Allies

which war are you talking about, am assuming your talking about ww2.

The western allies treated the defeated nations way better than the soviets.

The soviets after ww2 from 1945-1950 committed the Prussian German genocide which is never really talked about but never the less its how the soviets treated the Germans after the war.

there was a genocide and expulsion of 13.5 million Prussian Germans. The Soviets justified this because the Germans committed horrific atrocities during ww2. Japan was treated fairly decent but mainly western allies treated the occupied territory fair compared to the Soviets. The Russians were seeking revenge as 20 or more million Russians died during ww2.