Justice League Detroit and Secret Wars II were some of the worst, but the Captain Marvel who yelled "split" and his android body parts would split off is the worst in my opinion.
http://dialbforblog.com/archives/46/SPLIT! Reader, meet Captain Marvel! The character, an android, was created by Carl Burgos in 1966. (Burgos also created the original Human Torch, another android.) Cap's freakish power: the ability to split his own body parts from his body. Arms, legs, head, even fingers.
How did it work? Well, basically, Cap yells SPLIT to separate his parts, then yells XAM to call them back. Hence the designation "Split-Xam." The transformative words "Split-Xam" approximated the magic word that changed Billy Batson to the original Captain Marvel: SHAZAM!
I didn't mind 3D Man all that much and thought that he was somewhat interesting. The Fly was OK for me as well, and his origina wasn't any more absurd as any other character at that time. His grown up adventures as part of the actual Mighty Crusaders were by far worse.