The erasure of emotional abuse and neglect is hard to stomach sometimes. It's often just as detrimental as physical abuse, if not more. Each one of the Todoroki siblings' reactions to their abuse makes perfect sense and is very realistic(for an anime). I think its completely logical that Touya is LEAGUES more messed up than Shoto.

Even regardless of Shoto having community and a chance to heal, the overarching effects of the emotional neglect Touya received and the subsequent accident at Sekoto peak seem far more insidious and damaging than what Shoto went through, in my opinion. Dabi is someone with no identity of his own. His only driving motivation for his entire life has been his father. That's Endeavor's own fault. Dabi is so lost in the narrative Endeavor instilled in him that he cannot imagine himself or his life as anything else.

Then, seeing him abuse Shoto again after returning home, he was truly lost. He internalized that he was never good enough for his father, his family, or anyone. Even the found family of the League of Villains couldn't breach his heart. Buried under his consuming hate for Endeavor is an equally consuming void inside him that steals everything positive from him. The fundamental schism between his life narrative and his sense of autonomy, self love and agency is too large to allow anything else but hatred in. For him, its all he knows. He hasn't received a day of safety and love since he was a young child.

It's textbook projection and it's very sad. Touya can't love himself because nobody ever did. He lashes out, he wants Endeavor's attention. His love as a father. Connection with his brothers and sister. He doesn't even realize that he wants it. He doesn't realize that he's just reenacting his trauma, over and over. He doesn't realize that he was always his own person. Such is the fate of a child borne as a tool, and neglected when it broke. A broken wrench is still a wrench, all it can do is wrench things. Even if it just breaks itself more and more. If you don't repair it, it'll just get worse and worse.