Image: Rebel Wolves / Bandai NamcoOfficial screenshot from Rebel Wolves / Bandai Namco.
Uphill Battle is the hardest achievement in the game: finish the story on the Duelist preset without ever lowering or tweaking it. Only about 3% of players have it.
Start a new game on Duelist and leave every difficulty setting alone. Play through the main quests and reach a full ending. The trophy pops with the ending.
Choose Duelist from the very first screen. Do your trophy cleanup, such as Untouchable or Together Forever, on a different save so you never touch the settings on this one. Keep manual saves before big fights.