The antonyms for the phrase "slopes upwards" might differ depending on the context of usage. Some potential antonyms include "slopes downwards," "levels off," "remains flat," or "descends." If referring to a terrain, the antonyms could also be "descends sharply," "plummets," or "drops steeply." In terms of a graph or chart, the antonyms could consist of "declines," "falls," or "drops." Without context, it can be challenging to pinpoint the exact antonyms for this phrase. Nevertheless, it is crucial to understand these antonyms to communicate directionality effectively in a variety of settings.