From the UWF Writing Lab’s 101 Grammar Mini-Lessons Series Mini-Lesson #3
Bad Bad is an adjective used after sense verbs or after linking verbs. Example: I feel bad about missing your graduation. The food tastes bad. The child is bad.
Badly Badly is an adverb used after all other verbs. Example: Tom writes badly. The chef cooks badly. The child acts badly.
Good Test Sentence He smells bad because he smells badly. (He has an odor because he has no sense of smell.)
Examples If the underdog wants to win badly enough, he can defeat an opponent who is physically superior. The instructor felt bad about giving the students a “pop” quiz covering a chapter that they were not assigned. Missing the train, Joe felt bad about not being at the game. Though the company did well during the war, things have been going badly ever since. The team felt bad about losing the swimming meet.