^Probably just means that he was angry and bitter at the world. Now he's a demi-god so he doesn't really give a crap
Btw, I hope Kishi hasn't forgotten that Obito is also Sasuke's primary target for revenge. Hopefully Obito wont die to some secondary character. Sasuke's revenge is doomed to fail by shounen logic, but at least let him have
some of it.