remiss
careless, culpable, delinquent, derelict, dilatory, forgetful, heedless, inattentive, indifferent, lackadaisical, lax, neglectful, negligent, regardless, slack, slapdash, slipshod, sloppy (informal) slothful, slow, tardy, thoughtless, unmindful
Antonyms
attentive, careful, diligent, painstaking, scrupulous