Apparently marrying a trifling person is at least a big concern if you're willing to give an ultimatum for such.
"Hey. I want to spend my life with you and make a very big commitment to you but I don't know if you will fukk me over or not so sign these papers".
Seems idiotic/contradictory. If you have bad judgment on people, just don't get married. Pre-nups are never guaranteed to work anyway.
The concept of wasting my time on someone who I think will fukk me over seems stupid to me in the first place.