This is the 902nd most frequent Japanese word.
悪い
"Bad" or "wrong."
Here, "悪い" is used to indicate a negative quality, specifically describing the grades as being poor.
私の成績は悪いです。
My grades are bad.
In this sentence, "悪い" describes the weather condition as unfavorable or undesirable.
天気が悪いので、今日は外出しません。
The weather is bad, so I will not go out today.
Here, "悪い" conveys a moral judgment, indicating that the action of deceiving is ethically wrong or inappropriate.