In my experience, this has to be the grapevine pin - or versions of the grapevine.
Women have told me that any pin that forces them to spread their legs is the most embarrassing or humiliating, not to mention the discomfort / pain. When a girl is made to open her legs she is naturally in a position that she'd normally associate with intimacy in private, and that's a pretty humiliating thing to have forced upon you in a fight scenario. It makes her feel inelegant, out of control and vulnerable. Hugely satisfying for the winner and enjoyable for anyone watching of course