Crappy fit is a common illness of lots of minis... Worst I had in that regard was a Dark Elf Cold One Chariot... absolutely NO two parts fit together! the main axle was warped and bent on two planes, the railing of the platform left huge gaps... total desaster! But that\'s technicalities.
Worst concept for metal minis have to be the big three Tomb Kings minis: The Catapult is just a bitch to assemble with lots of heavy parts, so even pinning won\'t assure it\'s all in line with the rest.
The Giant has the same problem... you basically have to glue on both (single) legs at once, or the guy will have some really weird hip problems. And usually you\'re one arm short for that.
But the Scorpion takes the cake. Claws not counted, you have six (!) single, very thin legs to glue into very flat holes. He will probably only touch the ground wih three (max.) when you\'re done. And only two might actually fit on the base. Probably the main reason why people always assemble the scorpion as it were digging itself out of the ground... spares them the crap. This guy made me pop a vein. The catapult was more of a hassle, but the scorpion was just plain stupid.
/rant off
On the upside, I\'ve always enjoyed the versatility of the plastic Space Marines. Easy to clean, build and convert... But I play those guys, so I might be biased...