Slam-bang is an informal term that refers to something done with great force or intensity. Antonyms, on the other hand, are words that have opposite meanings. Some antonyms for slam-bang could be slow, gentle, or peaceful. If something is done slowly, it is not done with great force or intensity, which is the opposite of slam-bang. Similarly, if something is done gently, it is done in a calm and mild manner. Peaceful is another antonym to slam-bang, indicating that something is done in a tranquil or non-violent manner. Therefore, depending on the context, these words could be used as antonyms to slam-bang.