Almost every MHA fan knows the fan theory of Dabi is Todoroki Tōya, it’s so well known that it’s got to be the most famous fan theory in MHA. Due to the the popularity of this theory, I won’t go into the detail of how and why Dabi is Todoroki Tōya, but how he got his scars.
Today, as I was watching older episodes, I realized something I hadn’t noticed before, the location of Dabi’s scars. As we the viewer knows, Dabi has five visible scars. One on each eye, and arms, and a large one on his jaw/neck. On closer inspection, you realize that the scars (no doubt burn scars) are located on places where Endeavor has his flames. For asthetics, Endeavor keeps his flames on his face and his arms. My theory is that young Todoroki Tōya wanted to impress his father, or maybe he wanted to be like him, so he tried to copy Endeavor. We know from the manga that Tōya’s firepower is greater than Endeavor’s, but he inherited his mother’s weak constitution, which is why Endeavor deemed him a failure. What could have happened is that, Tōya attempted to use his flames to look like his father, but since his flames are hotter, and he’s weak, he burned himself. It’s also, possible that it’s after this incident that Endeavor realized Tōya is a failure, and Dabi ran away because of this.
Again this is only a fan theory, and I’m possibly wrong, but the location of Dabi’s burns can’t be a mere coincidence.