Synonyms that are in the dictionary are marked in green. Synonyms that are not in the dictionary are marked in red.
Antonyms that are in the dictionary are marked in green. Antonyms that are not in the dictionary are marked in red.
The Primal Knife is unlocked by hitting all 16 Clockwork Castellans in the game and can be purchased in the Bonus Content menu for 1000 CP.
Source: https://www.cbr.com/resident-evil-4-remake-infinite-ammo-weapon-unlock-guide/