SKIF BMP-3. Terrible fit, terrible engineering, terrible details, terrible instructions.
On the plus side, the basic shapes are right (once you get it all to fit), and turns into a very nice kit with a WHOLE LOTTA TLC!!
Here's my finished model, as it appeared in
Armour Modelling magazine:
That was two solid weeks of parts clean-up and repair, followed by a month and a half of putty, sandpaper, and scratchbuilding. I'm happy it made the mag, though!