Here are some possibilities:
Animal:
* Dog: If you're thinking of the animal, "dog" could be an opposite, as they are both common domestic animals.
* Rabbit: If you're focusing on the prey aspect of foxes, "rabbit" could be considered an opposite.
* Lion: If you're thinking of the predator aspect, "lion" could be a contrasting animal.
Personality:
* Honest: If you're thinking of the cunning and sly nature of foxes, "honest" could be considered the opposite.
* Naïve: "Naïve" could be the opposite if you're thinking of the fox's trickery and shrewdness.
* Trustworthy: "Trustworthy" could be an opposite of "fox" if you're thinking of its reputation for trickery.
Other:
* Vixen: This is the female version of fox, and while not technically opposite, it could be seen as a contrasting term.
So, the "opposite" of "fox" really depends on the context and what aspect of the word you're looking at.