calamity; disaster; catastrophe
Formal, often used in news reports for large-scale tragic events such as war, natural disasters, or severe accidents.
We must never repeat the calamity of war.
地震による惨禍は想像を絶するものだった。
The catastrophe caused by the earthquake was unimaginable.
惨禍 is a broader literary word for any terrible calamity or disaster, whereas 戦禍 specifically refers to the calamity caused by war.
Compound of 惨 (miserable, wretched) and 禍 (calamity, misfortune). The combination directly conveys a severe and tragic disaster.