Translation:Someone's ugliness does not need to be known by everyone.
In English, "ugliness" is more often used to talk about appearances. The word "keburukan" is used more often to talk about characters and thus translates more accurately to "flaws" in English.
Aha...okay...do you have another alternative as well ?
I would translate 'someone's flaws' as 'kekurangan seseorang'.
I think 'flaw' is too mild as a translation for 'keburukan'.
How about: 'badness', 'evilness', 'foulness', 'nastiness', 'wickedness', or something similar?
Or does that sound strange in English ?