* Simple: The earthquake was a calamity that devastated the entire city.
* Figurative: The loss of her job was a calamity for her family.
* Formal: The recent drought has been a calamity for farmers in the region.
* With a negative connotation: His decision to invest in that company turned out to be a calamity.
* With a positive spin: They survived the calamity and learned valuable lessons from the experience.
The choice of sentence will depend on the context you want to create.