opposite is an adjective
gently
"Often" and "frequently" are antonyms of "rarely".
One is "never," and another is "immediately and another is "on a dime."
'Generous' is an adjective and the opposite is 'miserly', which is also an adjective even though it ends in 'ly like many adverbs.
The noun 'opposite' is a singular, common, abstract noun; a word for a person or thing that is totally different from or the reverse of someone or something else; a word for 'antonym'; a word for a concept; a word for a thing.The word 'opposite' is also an adjective, an adverb, and a preposition.
The opposite of the adverb bitterly is sweetly.The word sweetly is also an adverb.
The opposite of the adverb firmly (securely) is loosely.*When used to mean forcefully or determinedly (e.g. firmly stated), the opposite could be gently, weakly, or waveringly.
The adverb "well" is the usual opposite of the adverb "badly." If "badly" is used to mean "extremely or greatly" the opposite could be "slightly." E.g. He was badly bruised./He was slightly bruised.
No, it is an adjective, the opposite of definite. The adverb form is indefinitely.
gently
Careful.
Roughly
Adverb does not actually have an antonym, but it might be an adjective: an adjective only modifies nouns and pronouns; an adverb modifies a verb, adjective, or another adverb.
The opposite of carefully is carelessly.Both carefully and carelessly are adverbs.
The opposite of politely is impolitely.Both politely and impolitely are adverbs.
Seldom, rarely, infrequently
The opposite of neatly is messily.Another opposite is ineffectively.Clumsily can also be an opposite of neatly.Neatly, messily, ineffectively and clumsily are all adverbs.