What language is hardest to learn?

It depends form which region you come from. For example for Italian it is easier to learn German, French, Spanish and other Latin based languages, but they will find it difficult to learn Chinese or any other oriental languages. Same applies to Korean or Japanese and other in this region, they will find it easy to learn Chinese and other languages from the region but they will find it difficult to learn Latin based languages. But to me practice makes a man perfect, if you practice any language of the world naturally you will learn it. And if you are really serious then you have to go the place where people speak language you try to learn. So the difficult is relative term so far as languages are concerned. I am learning Spanish and all you required to learn is skill to conjugate the verbs. But so much of conjugation of verbs is not there in English. So i think difficulty in learning the language is relative term but then it is practice which will make you learn anything in the world.