I've read up on this a bit, and really it depends on what your native language is. For native English speakers, they say that asian languages like Chinese, Japanese, and Korean are among the hardest. Personally, I think learning Arabic or Hebrew would be pretty difficult also!

The most hard language ever is Arabic, over 50% of Arabs make mistakes during speaking Arabic (Silly or not the fact is), for non Arabic native speakers there is for example over 500 names of lion and over 80 names of snake. - You can spend a whole year learning the names of only lion and snake !!!!!!!!

I think Arabic language

The most difficult language in the world to 'learn', would probably be a language that does not have a written form. A purely oral language would be the hardest to 'learn', since we need to learn from listening and speaking... only.

The most difficult language to learn is Arabic and Asian languages