There isn't a comparative form of "opposite" in the traditional sense. You could use phrases like "more different" or "less similar" to express a degree of opposition, but there's no single word equivalent.
Here's why:
* "Opposite" is an absolute term: It describes a complete and absolute difference, not a gradual one.
* Comparative forms imply gradation: Words like "bigger", "smaller", or "faster" imply a scale of comparison. "Opposite" doesn't operate on a scale; it's either opposite or not.
Let me know if you have any other words you'd like to explore!