
The circumstances for both of them are very different. Shouto never looked up to Endeavor, there wasn't a time that he looked at his father with admiration or hope, Touya did and he suffered because of it. The way he wasted aside like he had no value, for a child that is extremely overbearing. Im not saying Shouto didn't suffer, he did very much so but that does not diminish Touya's pain or his truama.

Touya wasn't abused & willingly wanted to do the training.
He looked up to Endeavor & to be tossed aside like that must've really mentally hit him..
Even if they did it for his own sake he didn't really understand that way.
He is in the wrong, but at the same time he isn't ?
Shoto was mentally stronger than him, and he got the chance to meet Midoriya.
Touya killed himself and became crazy..
I don't know who "saved" him but that person still got a huge impact on him..
What's more is that Dabi seem weirdly similar to Shigaraki in certain way.
As if he was still a child trapped in an adult body, as for his caprice & the extreme he take just to piss off his dad..
You know, thinking back, Shoto's been seriously abused. His father beat him during practices to toughen him up, his mother threw boiling water in his face, and just recently his eldest brother was in the process of burning him alive before being stopped. Yet strangely he hasn't become a mass murderer nor tried to kill Fuyumi and/or Natsuo.