Real people in the real world make decisions that lead to thousands of deaths in order to save even more lives. It is called war, and the people involved usually consider themselves good.I have an issue seeing a "good" person killing hundreds of thousands for an end; premeditatedly of course. I view, the needs of the many outweigh the few, as strictly LN territory. Good is much more trickier than anything else in a antagonist. Though, the philosophical discussions are the real treat of alignment, for me anyway.
This of course leads to the question of whether we are talking about an objective truth, or if we are asking what a person who thinks of themselves as LG might do.