General Antonyms:
* Fiasco: A complete failure.
* Disaster: A calamitous event.
* Debacle: A complete collapse or failure.
* Mishap: A minor misfortune.
* Setback: A temporary delay or defeat.
* Drought: A period of extreme dryness, often used to describe a lack of something positive.
Specific Antonyms:
* Bust: (in mining) a failure to find valuable minerals.
* Flop: A failure, especially of a commercial venture.
* Dry spell: A period of bad luck or lack of success.
Other Words:
* Scarcity: A lack of something.
* Shortage: A lack of something needed.
* Depletion: A reduction in something.
* Poverty: A state of being extremely poor.
The best antonym for "bonanza" depends on the specific context of your sentence. Consider the meaning you want to convey and choose the word that best fits.