The phrase "was remiss" indicates a failure to fulfill a responsibility, obligation, or duty. Antonyms for this phrase would include "was diligent," "was attentive," "was vigilant," and "was punctilious." These words describe a person who is conscientious and responsible, fulfilling their obligations to the best of their ability. While being remiss implies neglect or irresponsibility, being diligent or attentive implies dedication and focus on the task at hand. By contrast, while being remiss suggests a lack of attention to detail, being vigilant or punctilious suggests a careful and meticulous approach. Choosing to act in a diligent and attentive manner can help to avoid the negative consequences associated with being remiss.