What are the comparative and superlative forms of word curly?

The word "curly" is already in the comparative form. There is no separate comparative form of "curly".

However, you can use "curlier" to describe something that is more curly than something else. For example, "Her hair is curlier than his".

The superlative form is curliest, which means most curly. For example, "She has the curliest hair in the family."