General opposites:
* Diligent: Showing care and conscientiousness in one's work or duties.
* Careful: Paying attention to details and avoiding mistakes.
* Attentive: Paying close attention to something or someone.
* Responsible: Being accountable for one's actions and decisions.
* Thorough: Being complete and detailed in one's work.
Legal opposites:
* Intentional: Done with a specific purpose or plan.
* Willful: Done deliberately and with knowledge of the consequences.
* Gross negligence: A high degree of carelessness that shows a reckless disregard for the safety of others.
Other opposites:
* Alert: Being aware of one's surroundings and potential dangers.
* Mindful: Paying attention to the present moment and one's actions.
* Cautious: Being careful and avoiding risks.
The best opposite of "negligent" will depend on the specific situation and the intended meaning.