By far the most difficult kit I've ever built was the 1/35 Skif BMP-3 you can see down in my signature.
Terrible fit, massive sink holes, ejector pin marks, mold separation lines, partially molded parts, thick or no details in many places, and an extremely misleading instruction sheet (I usually refer to it as a "pack of lies") were just
SOME of the problems with this kit. I spent most of the build just cleaning and repairing parts!
As I was commissioned to build this kit and write an article about it for
Armour Modelling magazine (March 2004 issue, vol. 53), I didn't have the luxury of putting it aside to compose myself. Had to meet that deadline!
All grousing aside, as tough a build as it was, the overall shapes are right, and I'm very pleased with how it turned out.
However, I haven't built a single model since then!
Perhaps the struggle was too much for me??