일반 : 一般
So 일반 means the noun 'normal'? As in 'the new normal'? And 일반적 means the adjective 'normal'? And 일반적인 means the adverb 'normally'? I guess in the last case, the adverb can be used as an adjective.
일반적으로 makes a more distinct sense of what we would understand as an adverb (although that ending doesn't create grammatical adverbs in Korean).