What is the comparative and superlative form of word furiously?

"Furiously" is an adverb, and adverbs don't have comparative and superlative forms like adjectives do.

To express increasing degrees of intensity with "furiously," you'd use adverbs like:

* More furiously (comparative)

* Most furiously (superlative)

* Extremely furiously

* Incredibly furiously

* Wildly

* Ragingly

* Frantically

You could also try using a different word entirely to express the desired level of intensity.