The Guiness Book of World Records has recently recognized Abu Dhabi's Capital Gate Tower as the furthest leaning tower in the world. The Capital Gate Tower leans 18 degrees compared to Pisa's Leaning Tower slant of 4 degrees. The major difference: the Abu Dhabi structure was designed to lean, whereas, the Pisa tower started to slant with time. The Capital Gate Tower will house a five star hotel and offices. It is not yet complete, but it is scheduled to open by the end of the year.
I went driving around Abu Dhabi today. One of the things I did was view the Capital Gate Tower from different venues.
View from the road:
From these angles, the building slant is not as noticeable:
It is from this view that you see the more pronounced slant: