Here is the full list of all 10 Devil's Dungeon achievements.
Finish game on hard mode
Defeated Rosa for the first time
Defeated Amy for the first time
Defeated Enid for the first time
Defeated Lilly for the first time
Defeated Patti for the first time
Defeated Yoko for the first time
Defeated Gloria for the first time
Defeated Charity for the first time
Defeated Vera for the first time