kindness; a term dabi is unfamiliar with. he was never shown anything soft, gentle, or even nice his whole life. all he was meant to do was become a weapon for his father. all because of all might. all to be a stronger hero than all might. he's put all that aside. he can't show kindness. unless it's you; his child.
you were a random kid on the street he picked up and took in. it was wrong of him, he knows. but, you were struggling, too. despite only being under 10 years old, you had a bad childhood already. he could make it better. he will make it better. he's trying, at least. even if he's a villain, he wants you to live a good life. a better life than his was. he will raise you right. even if you will live in rundown buildings and a place filled with villains.
he can't let the todoroki cycle repeat. he won't be his father. he'll be a good one, a better father than his could ever be. sure, he has his own temperament issues, but he apologizes. only for you. only for his kid.