With regards to Soviet casualties, I thought the western allies faced enemy forces on the western front in 1917-18 that were as large as or even slightly larger than those faced by the Soviets on the eastern front yet their casualties were considerably lower than Soviet casualties.
Also, wasn’t Americas bloodies battle in the 1939-45 war the battle of the Bulge with over 19,000 combat deaths compared to around 12,520 combat deaths at Okinawa including those killed at sea.