'Happen what may' essentially means accepting whatever consequences that may come your way of a particular course of action or decision. Some synonyms for 'happen what may' can include 'come what may', 'regardless', 'no matter what', 'anyway', 'in any case', 'nevertheless', 'despite everything', 'at all events', and 'irrespective of'. Each of these synonyms expresses the concept of being prepared to face whatever challenges that may arise and persevere regardless of the outcome. Whether it is using 'come what may' to express a willingness to accept the unknown, or 'nevertheless' to express a tenacity to continue despite setbacks, these synonyms offer an individual different ways to express their mindset.