Choose the correct form of adverb for the given sentence:
He was found fighting ___________ for his life.

- Fiercely is an adverb that means in a powerful and destructive manner.
- Loudly is an adverb that means in a strong or emphatic manner.
- Mightily is an adverb that means to a great or impressive extent; enormously.
- Desperately is an adverb that means used to emphasize the extreme degree of something.

Hence, from the context of the sentence, the correct answer is 'Desperately'.
Complete Sentence: He was found fighting desperately for his life.