If one marries Mr. X under the assumption that he is a tzaddik (or rich or smart etc), but he is really a rasha,that marriage was done under a false understanding and is not valid and does not need a get to dissolve because it is nothing.
I, with two kosher witnesses in tow and a video camera approach the bride before the ketuba signing and ask the following: "You think your Fiance is a tzaddik and a desirable husband, but if he were the sort of person to refuse to grant a get when asked, would you not want to marry him?"
If she answers that she would not want to marry him if that were the case, and several years later the husband turns out to be a get refuser, is my evidence sufficient to demonstrate that the marriage was done under a false understanding? If not, what additional rigors are needed?
Apparently R'Moshe Feinstein ruled that these 3 conditions must be met to annul a marriage. The potential issue is that "being the sort of person to..." doesn't count as a preexisting condition (2).
(1) The woman must discover a serious defect present in her husband after they are married.
(2) That defect must have been present in the husband at the time of the marriage.
(3) The woman must have been unaware of the defect at the time of marriage