A tainted history is a tricky reason why you are not promoted. This is because most superiors live in the fear of history repeating itself. Tainted history can be anything from being involved in a major crime or a simple office misdemeanor such as inappropriate conduct towards colleagues or customers. You will have to work really hard to convince them that you have changed and there is no chance of your haunting past ever repeating itself. Showing and not just telling may just do the trick!