Cataclysm
Part of speech: noun
Definition: A sudden, violent event. A sudden and violent change in the earth's crust. A great flood.
Tragedy
Part of speech: noun
Definition: A drama or similar work, in which the main character is brought to ruin or otherwise suffers the extreme consequences of some tragic flaw or weakness of character.The genre of such works, and the art of producing them.A disastrous event, especially one involving great loss of life or injury.
Example sentence: There's no tragedy in life like the death of a child. Things never get back to the way they were.