carefully; thoroughly; closely
Used when examining, considering, or thinking about something with great care and attention.
After thinking it over very carefully, I decided to decline the offer.
Please check these documents very carefully before submitting them.
Emphasizes the degree of a state or quality; often used in negative or surprising contexts.
For him to say such a thing, something very unusual must have happened.
I can only say that it's extremely bad luck.
unavoidable; have no choice; cannot be helped
Used in set expressions like よくよくのこと or よくよくの事情 to indicate that a situation is beyond one's control or leaves no alternative.
Unless there are unavoidable circumstances, we cannot extend the deadline.
He must have had no choice but to quit the company.
I gave my reply only after thinking it over very carefully.
All I can say is that I've been extremely unlucky.
There must have been some unavoidable reason for it.
Looking closely, I saw that it was a fake.
非常に is a neutral, everyday intensifier for 'very', whereas よくよく in this sense often carries a nuance of surprise or negative circumstance.
仕方ない directly states that something cannot be helped, while よくよく in this sense implies a situation so dire that it leaves no alternative, often used with こと or 事情.
念入り is an adjectival noun meaning 'meticulous, careful', while よくよく is an adverb modifying verbs of thinking or looking.
よく simply means 'well' or 'often', while よくよく is an emphatic doubling used for careful examination, extreme degree, or unavoidable circumstances.
Standard kana spelling; the word is usually written in kana.
Rare kanji spelling; not commonly used.
Rare kanji spelling; not commonly used.
Rare kanji spelling; not commonly used.
Reduplication of よく (yoku), the adverbial form of 良い (yoi, 'good'). The repetition intensifies the meaning, leading to senses of 'very carefully', 'extremely', and 'unavoidably'.