Different countries (un)developed differently in WW2, depending on the year. US and UK grew quite a lot during the war, but GDP started to falter towards the end (keep in mind a lot of that was military and foodstuff aid, and in the US that led to shortages in the stores and budget deficits reaching as high as about 27% in yearly terms, as we don't have quarterly data available), despite the highest growth rates in the history of the country, and were somewhat depressed in the first years after it. Germany also made out relatively good before 1945, thanks to the looting from the countries it occupied, slave labor and military spending in general, before it fell by 29% in 1945 and nearly 53% in 1946.

Economies like France, Italy, Netherlands, Poland, Greece and obviously the USSR, were being exploited or utterly destroyed in the process, while other Nazi-occupied ones like Denmark, Norway and Belgium also suffered a lot at the beginning, but surprisingly grew during the 2nd half of the war.

https://ourworldindata.org/grapher/maddison-data-gdp-per-capita-in-2011us-single-benchmark?yScale=log&time=1805..1948&country=FRA~DEU~ITA~NLD~POL~OWID_USS~GBR

That'll tell you the effect (in GDP per capita) on those countries.