Responses

No, endeavor was already abusive when he was training shoto as at some point in the tournment arc you can see a flashback of him pushing shoto to train while touya, fuyumi and natsuo were playing together.
Also touya only died while their mother was hospitalized after spilling the hot water on shoto's face.
wait so endeavor initially started off as a pretty decent dad but touya just saw it as him giving up on him. touya's "death" was what caused him to become harsher to himself and his familu as well as abusive- comparing him and shoto in like a "my son tried so hard it caused his death, this kid wont get hurt by my flames but his efforts arent enough"