からこそEmphasized because, Precisely because

から expresses a reason or cause, similar to 'because of A, B' or 'A, so B' in English. The reason comes before から, with the result after. からこそ is the same から followed by the emphatic こそ, highlighting that the given reason is precisely or solely responsible for what follows. It's used for strong arguments or emphatic points.

あまり follows a noun or verb phrase and shows that an extreme state leads to an unintended result, e.g. 緊張のあまり声が出なかった ('I was so nervous I couldn't speak.') からこそ attaches after the reason and emphasizes it as the precise cause, e.g. 緊張したからこそ全力を出せた ('It was precisely because I was nervous that I gave it my all.')

Both use こそ for emphasis, but からこそ highlights a reason or cause, meaning 'precisely because', e.g. 努力したからこそできた ('I could do it precisely because I worked hard.'). こそ on its own emphasizes the word it follows, framing it as precisely the one, e.g. 彼こそできる ('He, if no one else, can do it.')