>>213581669
We know Light isn't a good person simply because of how he dealt with Naomi. Now you can argue that killing her was an act of self preservation. And that is fine. But he didn't just kill her. He gloated about it to her face. He relished in it. He enjoyed it.
He didn't lament the circumstances that caused him to have to get rid of her. Her didn't show any remorse for being "forced" to kill a non-criminal. He basically laughed about it. That is when Light dropped all pretenses of being a good person.