tragedy, disaster, collapse, downfall, cataclysm
A synonym for calamity could be disaster, catastrophe, or debacle.
Synonyms for calamity include misfortune, mishap, tragedy, disaster, or catastrophe.
calamity
Disaster
disaster
A synonym starting with d of the word calamity is 'disaster'
"Disaster" is probably the closest synonym, but "distress" rather close.
calamity, hazard, disaster, blow, collision
A synonym for the word "calamity" that starts with the letter "d" is "disaster." Both terms refer to significant and often sudden events that cause great damage, distress, or loss.
A disaster, like a calamity is a hugely problematic turn of events.
That word would be disaster.
One option is the word disaster.