I'm sure some awful online Flash game or single title in a Windows 3.1 "Best of Entertainment" compilation would claim that dubious distinction, but I'm having trouble remembering a specific example. For standalone commercial releases, Combat Air Patrol for DOS is a definite contender:
The lack of polish is shocking, even by the standards of 1995. In case you were wondering, no, your speakers aren't malfunctioning. There is absolutely no music or sound except for the occasional missile fire, explosion or switch toggle. If that wasn't bad enough you've got the absolutely horrid visuals, with dirty brown skies, awful draw distance and a terrain morphing "feature" that's downright disorienting. Of course, that's assuming the game didn't crash on you...which it would with alarming frequency.
Oh yeah, and you'd better not take the F-14 out on ground attack missions because you can't equip air-to-ground weapons...but the game sure as hell isn't going to tell you that. One could argue that any military aviation buff would know that, but gimme a break, I was a kid who didn't know any better. Even "dumb firing" air-to-air ordnance won't work, because they do no damage against ANY ground target. I HATE when combat flight games do that. Look, I know I'm not using my AIM-120s properly, but if it can rip apart planes, surely it would have a similar affect on "soft targets" like loaded Scud launchers, AA guns or munitions trucks?!
The most baffling thing of all is that people seemed to have LIKED this game back in the day, at least if comments on vintage gaming sites are any indication. I know it was the 90's and 3-D graphics were still in their infancy, but there were SO many better alternatives to choose from. Either people have a debilitating case of Nostalgia Goggles or they have it confused with the Amiga version, which I've heard is the superior product.