Q4W: What lie that a man tells you to get into a relationship/into your pants, would be seen as the biggest betrayal?

So e.g. the male equivalent most men would agree is if a woman claimed to be low count, but later into the relationship he finds out she was a huge whore, maybe did pay for play. Or even if she claimed to be a virgin, but he later found out she's been with a number of men.

So similarly if a man told you something before successfully taking you to bed, or getting into a relationship with you, what would he have to lie about to be seen as the biggest betrayal in your eyes?