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っぽいヘアスタイルだね。
Viet's hair style today kind of looks like a delinquent's, don't you think?
不良パーツが見つかりました。
The malfunctioning parts were found.
あの不良少女は、いきなり学校に来なくなったと思えば、ギャングに入ったそうなんです。
That delinquent girl suddenly stopped coming to school, and the next thing we knew, she had apparently joined a gang.