CHALLENGING Synonyms: 176 Similar and Opposite Words - Merriam-Webster
https://www.merriam-webster.com/thesaurus/challenging
WebSynonyms for CHALLENGING: difficult, tough, rigorous, demanding, hard, formidable, complicated, heavy; Antonyms of CHALLENGING: easy, simple, light, soft, effortless, clear, undemanding, cheap.
DA: 96 PA: 52 MOZ Rank: 34