Antonyms for the word "arch fiends" are words that stand for opposing meanings. Instead of "arch fiends," one could use antonyms such as "benevolent angels," "compassionate saints," "honorable heroes," or "virtuous do-gooders." These antonyms indicate positive qualities instead of the negative connotations associated with "arch fiends." While "arch fiends" evoke images of evil masterminds and dark forces, antonyms such as "benevolent angels" suggest purity, kindness, and good intentions. The use of antonyms is important in writing as it allows for a broader range of expression and can help to create a more nuanced and balanced narrative.