What is the comparative form of the word fiercely?

Fiercely is an adverb so first change it into a simple adjective. Fiercely -> Fierce. Comparative forms of adjectives are best defined positive or negative or between two objects/people/ideas.

Fierce, fiercer, fiercest, more fiercer, most fiercest <-- all the forms of the adjective. Hope I helped. ~yuri-candy, Answerer/Member