General Antonyms:
* Gradually: This implies a slow, steady progression.
* Slowly: Indicates a lack of haste.
* Smoothly: Implies a seamless, effortless transition.
* Gently: Suggests a kind and careful approach.
* Carefully: Emphasizes a deliberate and cautious manner.
More Specific Antonyms:
* Unexpectedly (opposite of "suddenly" which can be a synonym for "abruptly")
* Gradually (opposite of "suddenly" which can be a synonym for "abruptly")
* Carefully (opposite of "rashly" which can be a synonym for "abruptly")
* Thoughtfully (opposite of "impulsively" which can be a synonym for "abruptly")
Example:
* Abruptly: "He ended the conversation abruptly."
* Gradually: "The sun gradually set below the horizon."
* Carefully: "She carefully explained the instructions."
The best antonym will depend on the specific meaning you want to convey.