* Auspicious: Suggests good fortune or favorable signs.
* Favorable: Indicates a positive outcome or opportunity.
* Propitious: Means favorable, auspicious, and promising success.
* Hopeful: Expresses optimism and belief in a positive future.
* Encouraging: Inspires confidence and positivity.
* Benign: Means harmless, kind, and gentle, the opposite of threatening.
* Ordinary: Means typical and unremarkable, contrasting with the unusual or significant nature of a portent.
* Unremarkable: Similar to ordinary, implying a lack of significance.
The best antonym will depend on the specific context in which "portent" is used.