Night Creatures and Darkwing are crusty mustard play control-wise, but at least they're unique, they're games, and it's possible to get into them (of course, I think Hydlide and Deep Blue are decent games). I will agree that Night Creatures is the worst side-scrolling action game on the Turbo.
Bad games are:
Super Volleyball - controls are almost unplayable, one screen, almost no music.
Timeball - copyright 1983.
Falcon - it seems like Spectrum really set out to make an honest flight sim and I like how they took advantage of all the peripherals (TurboLink, backup RAM, included a TurboStick diagram in the manual), but this game sucks.
On other systems, I think Beast Wars N64 is the worst game I've ever played.