na-adjective, noun
malicious; vicious; underhanded
Describes actions, methods, or intent that are deliberately harmful, dishonest, or morally bad. Often used for crimes, business practices, or behavior.
悪質な手口で高齢者から金をだまし取った。
They swindled money from the elderly using malicious methods.
このサイトには悪質な広告が多い。
This site has a lot of malicious ads.
na-adjective, noun
shoddy; inferior; poor-quality
Refers to products, materials, or workmanship that are badly made or of low quality. Less common than the 'malicious' sense.
悪質な工事でマンションに欠陥が見つかった。
Defects were found in the apartment building due to shoddy construction.