Borg, Worf/Dura's/Civil war, and probably Q my favorites so I am right on trend. I think with the Civil War you need to expand and count Worf defending his father and the succession as well, plus Word and Alexander's mother. They tied all of those stories together extremely well.
I agree that the Klingon arc was probably the most well-written and well-developed continuing story on TNG.
It didn’t appeal to me personally....but that’s not because it wasn’t well written.