8. Leonard Part 6

In 1987 Bill Cosby, dangerously high on his mammoth success, released on of the most reviled films of all-time. A self-indulgent mess scant on laughs and big on tedium, Bill Cosby's 6th instalment in the imaginary Leonard series of spy films failed so badly that the world was spared the horror of Leonard part 7. Despite starring, producing and co-writing the feature, even Cosby wanted to smother his love child in the crib, publicly urging audiences not to waste their time on it and buying the television rights to ensure it never aired on TV. A glorified Coca-Cola commercial, produced by the Coca-Cola division of Columbia pictures, Leonard Part 6 remains a cautionary example that hubris and product placement can't produce a franchise no matter how hard they try.