전혀(jeon-hyeo, jeonhyeo)
전혀 means a complete negation, indicating absolutely nothing or not at all.
When to use
complete negation, strong negation emphasis, only in negative sentences
The nuance
전혀 is used mainly in negative sentences and never with affirmative ones; it can be combined with 조금도 for emphasis.
별로(byeol-ro, byeolro)
별로 expresses something less than expected or unsatisfactory, mostly used in negative sentences.
When to use
underwhelming evaluation, negative judgment, used with negative sentences
The nuance
별로 is used with negative sentences to mean 'not really' or 'not particularly'; rarely used in affirmative sentences.
조금도(jo-geum-do, jogeumdo)
조금도 emphasizes a very small amount or degree in negation.
When to use
quantity emphasis negation, strong negative sentence, used with 전혀
The nuance
조금도 is used only in negative sentences, often combined with 전혀 for strong negation.