The US Foreign Service has a scale of how difficult languages are for a native English speaker: https://www.atlasandboots.com/foreign-service-institute-languag

The US Foreign Service has a scale of how difficult languages are for a native English speaker: https://www.atlasandboots.com/foreign-service-institute-language-difficulty/ https://www.atlasandboots.com/foreign-service-institute-lang... Category V, requiring 2200 hours of study, has "languages which are exceptionally difficult for native English speakers" and consists of Arabic, *Japanese, Korean, Cantonese (Chinese) and Mandarin (Chinese), with the asterisk indicating that Japanese is considered the hardest of the lot. Obvious caveat: the Foreign Service only teaches languages useful for diplomats, meaning that obscure regional languages won't make the cut.