The answer to this question involves a paradox since you are talking about complexity, any object one might name would be less complex than making the sum of 2 of them, or making however many then connecting them, so to answer your question it is the most difficult man made thing that has been made as of today; the most complicated collaboration of complex things of course being this right here: the internet.
Sincerely the answer to your question.
What is the most difficult thing about being a cowboy
He never HAD to make anything...he had an idea that led him to create things
The language barrier is usually the most difficult aspect.
I think the most difficult thing Hillary Clinton face is to serve the nation while most people stone her with bad issues.
Einstein reportedly said that the most difficult thing to understand in the world is income tax.
dough
A cockroach.
I suppose that it would be to make sure that it was made correctly.
turning it on! lol
"most difficult" is a personal thing. What you find most difficult someone else might find easy and also, the other way around.
it has made unification difficult but can u answer why its made it difficult
getting the girl drunk enough