all characters from ironman & starwars.
Iron Man was alright before the release schedule became Iron Spam. He's been in at least one good film and produced some pretty nifty figures.
I think to calculate apex worthlessness, you need to consider a) screentime/recognisability of figure, b) actor/celebrity likeness involved, c) success of property figure is licensed from and d) aftermarket value.
On that basis Wong Ka Kui would score highly, but he's huge in Asia. Same goes for the various figures they've made based on Chinese movies, Japanese manga, etc.
I'd say Tonto has to be pretty high up the list. The Depp sculpt is rendered useless by the face paint, it's an unappealing design, the movie flopped and they couldn't even give the figure away at one point. Most of the b-list Iron Man suits that had less than 0.5 seconds screentime, and the cowboy Tony Stark. The Alien and Predator 'inspired' female figures too.
Maybe Captain Sao Feng from Pirates of the Caribbean for the top spot? I love Chow Yun Fat, but a figure of a borderline-racist yellow peril stereotype with a shaven head, Fu Manchu beard and deep facial scars is pretty useless even for custom fodder, his character had barely any screentime and he was in arguably the worst of the four films...