白眉 is one phrase we use to say “the best”, although if we took the kanji characters literally, it’d be translated as “white eyebrows.” Those two things seem pretty unrelated, let’s explore how they are connected!
The expression 白眉 is based on a person in Chinese history named Ma Liang. He had four brothers and all of them were known for their intelligence - and Ma Liang was the smartest among them. He was so wise that he had so many gray hairs (or 白髪 in Japanese) in his eyebrows. So we use Ma Liang famous “white eyebrows” as a symbol to mean “the best!”
白眉 should only be used when “the best” is referring to “the best of the best”, i.e. when other competition is also very strong, just like Ma’s brothers. If you are the best student in your class, but your classmates don’t do very well, then you cannot be 白眉, no matter how excellent you are, since your competition is not equally strong. However, if there are many excellent students in the class, and you are the best, like Ma Liang among his brothers, then you truly are 白眉.
Since 白眉 should be “the best of the best”, 白眉 cannot be used to just mean “the best part” of someone or something. So if we say “この映画の白眉は最後です”, or “The best part of this movie is the last scene”, then that has the connotation of that there are so many excellent things in this movie, and the last scene was the best of them all.
Cheese cake is the best cake in this pastry shop! [although the other cakes are also really good]
There are many good Japanese textbooks, but “Minna no nihongo” is the best.