Dabi's scars are one of the most haunting visual elements in 'My Hero Academia', and they tie deeply into his tragic backstory. From what's revealed in the manga, his burns are self-inflicted—a result of his own Quirk, 'Cremation', overheating his body. He wasn't born with the resistance to handle such intense flames, unlike Endeavor, who trained Shoto to withstand extreme heat. Dabi's body literally couldn't contain his power, and the scars are a physical manifestation of that failure.
The irony is brutal—his father's obsession with creating the 'perfect' heir led to Dabi being discarded, and when he tried to force his body to meet those impossible standards, it rebelled. Every time he uses his Quirk now, it's like reopening old wounds, both literally and metaphorically. The way Horikoshi designed his character makes you feel the weight of his pain just by looking at him.