There are twelve main bosses in Clair Obscur: Expedition 33 that are not optional and must be defeated in order to complete the main story. Many of these are Act 1 bosses, as the bosses in the later stages of the game are generally in optional areas, save a handful of pretty tough ones. As such, this list does not include any of the optional Chromatic Nevron enemies or side bosses in Clair Obscur. I've done my best at omitting major story spoilers from this list, but there will still be spoilers that reveal the main boss's names and locations.