General Antonyms:
* Impossibilities: This directly opposes the concept of possibility.
* Certainties: When something is certain, there are no other possibilities.
* Limitations: Limitations restrict possibilities.
* Constraints: Similar to limitations, constraints limit possibilities.
Contextual Antonyms:
* Unlikely: If something is unlikely, it is a less probable possibility.
* Improbable: Similar to unlikely, this suggests something is not a strong possibility.
* Infeasibility: This refers to something being impossible to achieve or carry out, effectively removing it from the realm of possibilities.
The best antonym for "possibilities" will depend on the specific context and the intended meaning.