Bad
Substandard, Delinquent
noun, な adjective, の adjective
Something that's not good is bad or substandard. This usage is more formal and frequently paired with other kanji compounds. Alternatively, it can refer to someone who is a delinquent, in which case it is often used as a standalone word.
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
ビエト、今日はちょっと不良な感じのかみがただね。
It feels like Viet kind of has bad-boy hair today, don't you think?
ひんしつ不良のポテトチップスが半額で売ってたので買って食べたらおなかをこわしました。
Substandard potato chips were sold at half price, so I bought one and ate it. Then I got diarrhea.
あの不良少女は、急に成績が大幅に下がった後、ギャングの一員になったんです。
That delinquent girl’s grades suddenly dropped drastically and then she joined a gang.