this bad이 means “this,” and 나쁜 is the adjective form of 나쁘다 (“to be bad”), used before a noun. In the example sentences, the relevant expression is 나쁜 without 이.
KO: 이 나쁜 습관을 고쳐야 해요.
EN: I need to break this bad habit.
phraseRare#13,622
this badUsually comes before a noun, especially in insults or complaints, like 이 나쁜 놈.