40. 'Howard the Duck'
This 1986 effort — the first theatrical Marvel film aside from that Captain America serial 42 years earlier — was a creative and commercial disaster that not even producer George Lucas could save. The problem was that it was supposed to be animated, but contractual obligations forced it to become a live-action movie — specifically, an unfunny, effects-driven, story-deprived live-action film about a talking duck. Not a good way to start a multi-billion-dollar brand.