Antonyms of punctilious :
Examples of usage:
The new District Judge returned Colonel Starbottle's profoundly punctilious bow. "Openings in the Old Trail", Bret Harte.
The conclusive condemnation of all the crowd of punctilious restrictions of which the Apostle has been speaking lies in the fact that, however they may correspond to men's mistaken notions, and so seem to be the dictate of wisdom, they " are not of any value against the indulgence of the flesh." "The Expositor's Bible: Colossians and Philemon", Alexander Maclaren.
Therefore, is should be are; thus, " The gentry are punctilious in their etiquette." "The Grammar of English Grammars", Goold Brown.