i mean, i don't stand for killing innocent people. but touya isn't a good person, we all know that. the only thing he wants, is retribution for endeavor. however way he gets it, he doesn't care. he just wants him to suffer. cause he only got his hate fore his father. it's the only thing he knows and has. hate. he's not sane, he's not good.
he's completely unstable and rightfully so, he has never had any help, he doesn't even want it. he's gonna die sooner or later because his quirk destoys him, so he wants to see endeavor's downfall before that. all of that, because it's the only thing he has and knows, hate.
it doesn't justify his action, but just choosing good and bad like that doesn't work, cause he doesn't even care about good and bad
That's why I'm so upset at him. He doesn't have any clear goal just like how Stein said about all "fake" hero and villain alike.
He wants Endeavor to suffer, but doesn't care how and who is involved. Touya said to Hawk that he will carry on Stein's will, but everything he does goes against it.
And like u said, he is unstable and no one was there to help him. I get it, he has every right to seek revenge and hate Endeavor. But the way he does it? Just straight out no!!!

Yes, Endeavor was an evil, good for nothing father. However! That is still not an excuse to kill people, INNOCENT PEOPLE!
YOU WERE NOT THE ONLY ONE SUFFERING!
HOW DARE YOU DRAG OTHERS TO HELL WITH YOU WHEN THEY DON'T DESERVE!
And you know what else? Unlike every prick of a worthless father, at least Endeavor knew he was a piece of shit, and admits it, and did not beg for their forgiveness because it was too late! He did what he could to keep the remaining of his family intact while excluding himself!
Touya, I get that you went through shit, I get it. Everyone of your family did, but they haven't fucken kill a single innocent person! (╬ ̄皿 ̄)凸