Ukraine has lost over 800,000 troops and civilians
800,000 Ukrainian casualties is a wildly inflated figure. Per the United Nations:
Total civilian casualties
From 24 February 2022, which marked the start of the large-scale armed attack by the Russian Federation, to 10 September 2023, OHCHR recorded 27,149 civilian casualties in the country: 9,614 killed and 17,535 injured.
https://www.ohchr.org/en/news/2023/09/ukraine-civilian-casualty-update-11-september-2023#:~:text=Total%20civilian%20casualties,9%2C614%20killed%20and%2017%2C535%20injured.
Per The New York Times:
Russia’s military casualties, the officials said, are approaching 300,000. The number includes as many as 120,000 deaths and 170,000 to 180,000 injured troops. The Russian numbers dwarf the Ukrainian figures, which the officials put at close to 70,000 killed and 100,000 to 120,000 wounded
https://www.nytimes.com/2023/08/18/us/politics/ukraine-russia-war-casualties.html#:~:text=The%20number%20includes%20as%20many,and%20100%2C000%20to%20120%2C000%20wounded.
So total Ukrainian casualties now stand close to 220,000.
Of course, real casualty numbers could be much higher, especially on the Russian side since they are trying to hide their losses.