✔ 最佳答案
(以學術/ 認真角度作答)
不少人會認為包括中文, 日文, 韓文, 阿拉伯語, 匈牙利語等,
但若連語言學家也認為最難學的有巴斯克語 (Basque) 和美國阿拉斯加一個原住民用語: Tlingit (Tlingit language is well known not only for its complex grammar and sound system but also for using certain phonemes which are not heard in almost any other language. )