The only way Trump wins is if Hillary collapses due to scandal. If she avoids that, then she can't possibly lose to him.
Hillary is a terrible candidate, and almost any Republican could beat her. But Trump is so universally reviled outside of those 10 million or so people who love him, that he's the one person she would almost certainly beat. Barring a scandal that puts Hillary even worse shape than Trump, the election will have record-low turnout, and still have Hillary beating Trump by record margins.