As adverbs the difference between vehemently and ferociously
is that vehemently is in a vehement manner; expressing with a strong or forceful attitude while ferociously is in a ferocious manner, particularly violent and aggressive.
As adverbs the difference between confidently and vehemently
is that confidently is in a confident manner; with confidence; with strong assurance; positively while vehemently is in a vehement manner; expressing with a strong or forceful attitude.