My Hero Academia's Dabi was a mysterious character for a while. His aloof demeanor and astute mind made him a formidable foe for the heroes. Apart from his name, he did not disclose anything else until his identity was revealed in season 6's 11th episode titled "Dabi's Dance".
Dabi was, as many My Hero Academia fans suspected, one of Endeavor's sons, Touya Todoroki. Dubbed a failure by his father and driven insane by the aim to please him, he ended up burning himself alive.
With everyone thinking he was dead, Touya reinvented himself as Dabi and joined the League of Villains. Since then, he made it his goal to exact revenge from his father and make him suffer for what he had done. On that note, here is every hint at Dabi's true identity up to Season 6 Episode 11.
My Hero Academia: Every hint at Dabi's true identity up to Dabi's Dance
1) Physical features
In My Hero Academia, the facial features of Dabi were a lot like those of the Todoroki family. His hair, although dyed black, closely resembled a young Endeavor's hairstyle.
His turquoise eyes were the same as the Todorokis. This eye color was unique to their family, specifically Endeavor's side, with his own being a greenish blue. Other than him, Fuyumi and Shoto had the same color left eye.
The anime confirmed this fact. Furthermore, given that blue eyes are normally recessive and Rei's were grey, it appeared that blue was the dominant one and their children possessed them.
2) Quirk - Cremation
Dabi's Quirk Cremation gave him some of the hottest flames in My Hero Academia, burning at a temperature of at least 2,000°C (3,632°F). Powered by his hatred and rage, his flames burned hotter the angrier he got. While it can be argued that not every flame user is related to the Todoroki family, Dabi's are unique.
Going back to Endeavor, he wanted to create the perfect offspring who could combine his and his wife's Quirks to counteract overheating using ice. Dabi's flames were blue because of a chemical reaction rather than temperature.
Rei most likely produced ice, thanks to the liquid nitrogen in her body. When used with flames, it burned bright blue due to a reaction with carbon and nitrogen. So, when Dabi was born, her and Endeavor's genes combined but did not balance out. Hence, his flames were blue instead of orange-red like Shoto.
3) Fighting style
Debatable, but worth looking at. It was mentioned that Endeavor subjected Dabi to harsh training to make him capable of surpassing My Hero Academia's Number 1 Hero, All Might. As a result, he clearly taught him to fight the way he did, preferably at a distance at first, then closer later.
Even Shoto fights at long range, utilizing his ice side and, gradually, his flame side. This is most likely due to Endeavor's training as well. As a result, this serves as yet another clue to Dabi's identity.
4) Adopting Stain's belief
My Hero Academia's Stain was a villain and ex-vigilante who had killed a number of Pro-Heroes. This earned him the name Hero Killer. He was adamant that those who became Heroes for the sake of money and fame were unworthy of the Hero title. As a result, he took it upon himself to hunt down these "imposters" and cleanse the society of false heroes.
All Might was the only one he recognized because he always had a smile on his face and did everything he could to help people. Dabi supported his ideal of ridding society of fake Heroes, such as his father. He was the epitome of a Hero pressed under the weight of glory and ego rather than doing good for the sake of doing good.
In fact, that was precisely what the Endeavor was. Thus, he set fire to himself in an effort to appease his father. He went by the name Dabi after deciding to fake his own death and join the villainous underworld (translated to the word "Cremation").
5) Interaction with family and Heroes
Dabi's interactions with his family and other Pro-Heroes were also indicators of his identity in My Hero Academia. When he first met Shoto and Endeavor, he addressed them by their full names, Shoto Todoroki and Enji Todoroki, as if he had a personal connection with each of them.
After saving Twice from Hawks in My Hero Academia season 6, he also addressed him by his given name, which caught the Wing Hero off guard. That's probably when Hawks began to suspect who the villain was.
6) Frail constitution
He may have inherited his mother's vulnerability to fire, in addition to inheriting his parents' genes, albeit unbalanced. This explains why he isn't able to use his Quirk as effectively as he would like. Furthermore, he was most likely born with an illness that left him frail.
He is significantly smaller than Natsuo and Fuyumi when he is seen as a child standing alongside them. Years later, Dabi from My Hero Academia is still frail and has a weak constitution, which is probably why he fights at long range and only for a short period of time.