lit. change to more severe (idiom); to become more intense (esp. of shortcoming)
to aggravate
to intensify
Definitions (粵典–words.hk)
動詞
情況變得比本來更加嚴重 aggravation of a bad situation; a bad situation deteriorates
如果小朋友做錯事冇人糾正佢,以後就會變本加厲,唔知對錯㗎喇。
如果小朋友做错事冇人纠正佢,以后就会变本加厉,唔知对错㗎喇。
jyu4 gwo2 siu2 pang4 jau5 zou6 co3 si6 mou5 jan4 dau2 zing3 keoi5, ji5 hau6 zau6 wui5 bin3 bun2 gaa1 lai6, m4 zi1 deoi3 co3 gaa3 laa3. If children are not corrected when they do something wrong, then it will just get worse; the children will not be able to tell right from wrong.
Definitions (Wiktionary)
verb
to get worse; to become aggravated; to intensify one's effort to do something wrong