Many optional boss fights in Clair Obscur: Expedition 33 are as challenging as the main story bosses, if not more so. The Chromatic Danseuse is a dangerous optional boss that manifests two more mirror versions of itself, so you're essentially fighting three at once. It alternates between fire and ice, as well as attack and defense. On top of that, it's extremely difficult to parry and dodge when it strikes multiple times in succession, and it can do a lot of damage.