I've been slapped, punched, kicked, and hit with all kinds of things by a dual or two or three that (understandably though wrongfully) thought I was cheating on them. But, at the time, I never really saw it as abuse because 1.) I wasn't actually hurt or scared; I'm much bigger/stronger than they are and didn't feel powerless, 2.) have ties to a culture where expressed anger and "getting physical" is somewhat normative, 3.) theoretically, duality allegedly orients us towards sympathy, forgiveness and looking past grievances big and small, and 4.) my Quadra, in part due to valuing Se (the show of will and force) that acts based on valued Fi (deep conviction), is predisposed to various forms of power displays and "turn up," according to Strat >

Gamma Quadra types (especially, sensing ones, SEE and ESI) immediately lose control over themselves and will undertake anything to destroy their tormentor both morally and physically. (Such abuse Gamma types won't forgive to anyone!) Gamma Quadra will put to use all of their resources, all the materials at hand (up to sharp or cutting objects), but won't let the offender get away unpunished. The desire to put one's fists to use and beat the tormentor to death (or even tear him apart with bare hands) in such moments is overwhelming, thus the attack may be very brutal and fast.
All things considered, I'd think duality (followed by other more cognitively compatible IRs [most likely intra quadra ITR]) might present a situation where one is inclined to stay in an abusive relationship. My parents (SEE and LIE) were rather mentally and verbally abusive towards each other and to a lesser extent, me, as far as placing me in dangerous situations (allegedly for my betterment) that were grossly inappropriate for a child. What makes me think that cognitive compatibility is key towards healing, or at the very least, tolerating certain types of seemingly untreatable wounds is that we all still loved and constantly forgave each other. For a long time, and certainly before learning about Socionics, it was hard for me to reconcile the affection I was able maintain for those who objectively did me wrong and caused much harm--I almost felt as if I were being weak and dumb because I didn't definitively cut them off. But, in addition to the role my wonky Fi played (by either not valuing a relationship whatsoever or hyper valuing it to my detriment), the common denominator in my acceptance and forgiveness of abuse was a highly favorable, compatible IR, especially towards those within my own Quadra.

Theoretically, it makes sense that those sharing the same or similar function stacking and strength (identity and mirror) might possess more empathy and sympathy towards the expression of certain shared thought patterns and behaviors (maladaptive or otherwise) and those who are strong where their partners are weak (activity and duality) might hold more subconscious sway over each other's vulnerable judgment and perception functions, thereby causing confusion, dependence, complacency and indulgence where perhaps there shouldn't be.