What is the most difficult writing system to learn?

As a native speaker of English, I think that English is very difficult to learn. The alphabet is easy to memorize and hard to use in English. I before E except after C, there is no protein in caffeine, English spelling is weird. Is that enough, are we through?

Chinese is great fun to learn, especially if you learn Traditional characters. Traditional characters have an inner logic that has built up over millennia, and you absorb as you write. If you pay attention, you also learn a lot about sounds.

I have never studied Thai, but I have heard that Thai is very difficult to learn to write. Arabic is beautiful and looks difficult; I don’t know whether or not it is.

I found this beautiful Arabic calligraphy online. I have no idea what it says.