Brute

Optional, and soft-missable - this isn't on the main path. Brute is a Wasteland boss tied to a Xion scavenger side quest, so it locks with the rest of the Xion content once you let Adam take you onward after Abyss Levoire. Clear it during your Xion sweep. Parry the heavy swings, dodge the unblockable charge. (If you do miss it, it's recoverable in NG+.)