What is the superlative form of cosmopolitan?

There isn't a universally accepted superlative form of "cosmopolitan". This is because "cosmopolitan" itself describes a quality or state, not something that can be compared in degrees.

Here's why:

* "Cosmopolitan" means: "familiar with and at ease in many different cultures and societies." It's a descriptor, not a quantifiable attribute.

* Superlatives are for comparison: Superlatives like "biggest," "best," "most beautiful" are used to compare things within a group. "Cosmopolitan" doesn't imply a spectrum of degrees.

Alternatives:

If you want to express the idea of being *extremely* cosmopolitan, you could consider:

* Highly cosmopolitan: Emphasizes the extent of their cosmopolitan nature.

* Ultra-cosmopolitan: Adds a stronger, more extreme connotation.

* A true cosmopolitan: Highlights their authenticity and genuineness.

Ultimately, the best choice depends on the specific context and desired effect.