General opposites:
* Curse: A boon is a blessing or benefit, while a curse is a misfortune or evil.
* Hindrance: A boon helps, while a hindrance obstructs or prevents.
* Burden: A boon is a good thing, while a burden is a heavy or troublesome weight.
* Bane: A boon is a benefit, while a bane is something that causes harm.
More specific opposites:
* Disadvantage: If "boon" refers to a favorable circumstance, the opposite could be a disadvantage.
* Loss: If "boon" refers to a gain, the opposite could be a loss.
* Detriment: If "boon" refers to something beneficial, the opposite could be something detrimental.
Example:
* "The new law was a boon for small businesses." The opposite could be "The new law was a bane for small businesses."
It's important to consider the specific context to choose the most accurate opposite of "boon".