Story Related. Defeat the 2nd Boss
Shout Out to CLARION85 for the Tip!
There is a Hardcore Achievement for Completing the Game on Hardcore Difficulty. (One Hit Death)
HOWEVER, you can play the game on Normal all the way to the Last Boss and then quit to the Main Menu. Turn on Hardcore. The Achievement WILL STILL pop after you beat the boss on Hardcore. MUCH easier than playing the Full Game on Hardcore💪VIDEO GUIDE: