Vayeitzei, Breishis 29:19. Lavan as a Mechuton.

When Yaakov asked Lavan for the hand of his daughter Rachel, the passuk in 29:19 has Lavan saying " טוב תיתי אותה לך מתיתי אותה לאיש אחר", better that I give her to you than give her to some other person. The Likutei Yehudah brings from his uncle, the Piltzer (a grandson of the Chidushei HaR'im), the following pshat. Lavan knew that Rachel was a tzadeikes. So he said, if I give her to some other man, one of my resha’im friends, she might make him into a tzadik, and that would be a terrible waste. Why spoil a perfectly good rasha? It would be better for me to give her to Yaakov, who is a tzadik anyway.

This reminds me of how I felt about a certain shidduch that was suggested for one of my daughters; I had known the boy’s father for many years, having met him in Yeshiva, and we disliked each other from the day we first met. Maybe that’s an overstatement; it is more that I couldn't stand him, and he viewed me as beneath liking or disliking. The reason he was interested in the shidduch was basically my daugher's yichus and special personal attributes, which apparently outweighed whatever contemptible traits I brought to the table. So when the shidduch was suggested, I decided that I might as well take him for a mechutan since I already don’t like him, instead of wasting another person I might otherwise like on being my mechutan.

As it turned out, the kids met, and got married. His positive qualities as a father in law more than make up for the 'imperfections' in his personality. What’s the mussar haskeil? That two negatives make a positive? That I had assessed him incorrectly? That he grew up and changed? Or that I grew up and changed? Or maybe that in analyzing options, my advice is like my mother's sense of direction-- you ask her which direction to go, and go the opposite way, and you'll get there? I don’t know.

Yenta, in a comment, sent a link to a sefer called Noam Megadim that says this pshat with even more acerbity, and it can be found here on Parshas Mikeitz.