bad

1250–1300; Middle English badde, perhaps akin to Old English bæddel hermaphrodite, bædling womanish man

2. Bad, evil, ill, wicked are closest in meaning in reference to that which is lacking in moral qualities or is actually vicious and reprehensible. Bad is the broadest and simplest term: a bad man; bad habits. Evil applies to that which violates or leads to the violation of moral law: evil practices. Ill now appears mainly in certain fixed expressions, with a milder implication than that in evil: ill will; ill-natured. Wicked implies willful and determined doing of what is very wrong: a wicked plan.

The adjective bad meaning “unpleasant, unattractive, unfavorable, spoiled, etc.,” is the usual form to follow such copulative verbs as sound, smell, look, and taste: After the rainstorm the water tasted bad. The coach says the locker room smells bad. After the copulative verb feel, the adjective badly in reference to physical or emotional states is also used and is standard, although bad is more common in formal writing: I feel bad from overeating. She felt badly about her friend's misfortune.
When the adverbial use is required, badly is standard with all verbs: She reacted badly to the criticism. Bad as an adverb appears mainly in informal contexts: I didn't do too bad on the tests. He wants money so bad it hurts. See also badly, good.