Disaster
A synonym starting with d of the word calamity is 'disaster'
disaster
"Disaster" is probably the closest synonym, but "distress" rather close.
One option is the word disaster.
That word would be disaster.
A disaster, like a calamity is a hugely problematic turn of events.
Dazzling is a synonym for beautiful. Delightful is another word for beautiful.
dire
Deluge
Disaster?
(D) Unknow
declared