Probably not the worst ever, but the Bill Peterson-led Houston Oilers (1972-1973) were pretty pathetic. There is a book by Bill Curry written with George Plimpton I cannot recall the name of in which Curry goes into some detail about playing for the Oilers and Peterson back then. Pretty amazing. The Oilers not only went 1-13 in both years but, with Peterson calling the shots, they might have actually been lucky to get the wins they did.