noun
Refers to a deeply ingrained negative behavior or custom, often with moral overtones. Can be used for personal habits or societal ills.
喫煙は悪習慣だと多くの人が考えている。
Many people consider smoking a bad habit.
その村では古い悪習慣がまだ残っている。
Old evil practices still remain in that village.
習慣 is a neutral 'habit' or 'custom', whereas 悪習慣 explicitly denotes a bad one.
Compound of 悪 (bad) + 習慣 (habit/custom). The exact historical derivation is uncertain, but the word follows a common Sino-Japanese compounding pattern.