* Careful: This is the most direct opposite, meaning paying attention to detail and avoiding mistakes.
* Thoughtful: This implies considering the potential consequences of actions.
* Mindful: This emphasizes being aware of the present moment and surroundings.
* Diligent: This highlights persistence and effort in doing something thoroughly.
* Attentive: This means paying close attention to something or someone.
* Conscientious: This implies a strong sense of duty and responsibility.
The best opposite word will depend on the specific situation and what aspect of carelessness you want to contrast.