Why was World War 2 a terrible war?

World War II was a devastating conflict marked by unprecedented destruction, with an estimated 70-85 million fatalities, including the genocide of six million Jews in the Holocaust. The war saw widespread atrocities and suffering, including bombings of civilian populations and the use of atomic weapons on Hiroshima and Nagasaki. Additionally, it resulted in significant economic turmoil and displacement, reshaping global politics and society for generations to come. The scale of the human and cultural loss, combined with the ethical implications of the war's conduct, underscore its classification as a terrible war.