Easily the 1/48th Aurora P-61... Grossly out of scale (more like 1/43rd), no detail to speak of, that which was there was totally an afterthought and the radials's jugs were scribed into the molds with what looks like a dental burr, gear doors molded shut but the struts still were inserted into the nacelles and fuselage, and typical pilot head/shoulders molded into the non-cockpits, covered with a frosted canopy, and the insignia and serials molded in as well...
However, if you wanted a 1/48th Black Widow before the Monogram kit was released, it was the only game in town...
Just to add my own comment about what Fermis said regarding the ModelCraft F-82... Easily the toughest kit I ever built, but not the worst... Once the sanding was done, the kit went together quite well and actually thought mine turned out pretty good, even if I am saying so m'self... It lent itself to superdetailing quite well, with little need for aftermarket parts, unless you wanted them... I got away with just building the throttle quadrants and O2 hoses & regulators and vac-forming new canopies and windscreens...I thought I was going to have to use the gear struts from the Monogram P-47D Bubble-top, but it turned out that I was able to clean up the kit parts...