D-Day but it was over twice the numbers. The Allied invasion of Sicily actually outnumbered D-Day but was far less contended.
In the Pacific, Tarawa was comparable in numbers, Operation Forager, (Mariana and Palau Islands) 128,000 men.Iwo Jima was 110,000., Okinawa was an astounding 250,000.
Guadalcanal was 60,000, a bit larger than Inchon with 40,000 in the landings but 75,000 involved in the operation.. That is about the most comparable in terms of numbers.
The Inchon landings themselves had a very low casualty rate. You just didn't get that in WW2 landings. the Inchon campaign was very successful and retook Seoul from the Communists.