Dabi, definitely.

Dabi's basically stuck in a metal sarcophagus that he needs to be in or else he'll die.

Overhaul's was more damaging mentally than physically, if you ask me, although living without his arms is still bad.

@Piccolo Machiavelli You make it sound like Dabi became Darth Vader. Dabi at least has his family to support him. Overhaul has zero sympathy from anyone, including the person he idolized. And he doesn't have his arms.

Dabi hated his family and blamed them for his despair. He wouldn’t want their support.