hands down English becuz we have sooo many rules that other languages dont have and all the silent letters and blah blah blah! i feel soo sorry for my english language learner students..English is hella confusing!
Majority of the world population use ENGLISH and some how use and understand it but there are many languages which are not spoken and written in the world as English is. So Chinese is the other language which is very difficult to read and write. ARABIC, FRENCH AND RUSSIAN ARE OTHER LANGUAGES WHICH are difficult to learn.
Japanese would be the hardest for an english speaking person to learn, in my opinion, however, for a other-language speaking person, English is the renowned impossible language- simply because our language has tons and tons of exceptions, and not a single rule that is ALWAYS true. And, because its a mix of hundreds of other languages. Well, 10's.
I've read that Japanese is the hardest for an English-speaker to learn because there are so many words that have multiple meanings depending on the inflection. For anyone else, English is the hardest to learn, mainly because we have more irregular verbs than any other language.
Chinese then Korean. But Japanese is easier than English though. Just to point things out. Chinese has a huge alphabet and different way to pronouns things and multi-symbol. Japanese is easy to spell and understand my single symbol.
I always consider Chinese is most difficult language, because Chinese words're combined by Chinese characters, Chinese has too thousands of characters,oh my god!!! and you need them to make vast majority Chinese word, what language can challenge with Chinese??!!!!
It all depends on how passionate you are about the language. If you care to learn a language and you motivate yourself in the culture then it becomes easier. I failed spanish in school. It's not so much that it was hard.. it just wouldn't stick with me and I couldn't learn it because I didn't care for it. But for my job I work as a tourists and we get many japanese customers.. I have been working there for 3 months now and can pretty much understand what they are saying to me and I can speak to them on basic terms.