For me, it has to be Korean (Hangul is easy to grasp) but the pronounciation, my god: it’s like I can’t understand a word being said when they speak (while that part is manageable in listening to spoken Japanese). Maybe it’s just me not having the “trained” ear on listening to Korean phonology in real time whilst learning the language.
Yeah, the difference between what you learn in school and how natives speak is often huge in Spanish. I feel like in French (which I never learned, but I’ve seen/heard quite a few radio and tv broadcasts), the speech is much more formalized and separated - yeah the orthography is bonkers, but the rules are clear and it’s relatively clearly separated words instead of Spanish’s syllable stream.