Jar Jar Binks
An attempt to create a 'comic relief' character which backfired badly, turning the Star Wars film Phantom Menace into little more than a cross between a farce and a special-effects laden episode of Love Thy Neighbour.  Binks is an alien who, for reasons I'm sure won't be apparent to anyone but all-seeing higher beings, talks like a dated black stereotype.  Ah, but C3P0 and R2-D2 were comical characters, the fanboys point out.  Yes, but they actually served some function in A New Hope, and if they're comic characters then why do we need yet another 'comic' character.
Jar Jar Binks, just one of the many things wrong with a film with was nothing really more than one long advert for toys, video games, happy meals and various other tat.  But it's still worth mentioning that Jar Jar Binks is a shit creation and a total wanker.