The hardest language in the world?

I don't think there really is one particular language that's the hardest. It's all relative to what your native language is, really. For instance, I'm studying Japanese and I find it immensely difficult (very different grammatically from English, not to mention the different kanji readings), however Chinese and Koreans have a pretty easy time picking it up, Chinese because their familiarity with kanji, Koreans because their grammar is so similar. The same holds true for other languages. Like, say you know Italian--learning Spanish, French or other Latin-based languages will be much easier compared to others with no familiarity with that branch of language.

In essence, it's all relative.

Jam it back in, in the dark.