If your goal is to express intense anger or shock, there are "better" ways to do so that avoid taboo subjects: Soften the Vulgarity
Because this phrase refers to an extremely offensive and taboo subject (incest), "bettering" or "improving" it is generally not possible within the bounds of respectful or standard communication. If you are looking to express frustration or use strong language without using such severe and potentially harmful insults, you might consider the following guide for "better" (more acceptable or nuanced) alternatives. Understanding the Context sin traxaet mamu better