This is a complex ethical dilemma without a clear right answer. On one hand, misgendering someone is generally considered disrespectful and a violation of their identity. It can cause significant harm and distress. Ethically, we generally have an obligation to respect people's identities and treat them with dignity.

On the other hand, if the alternative is the loss of one million lives, that is an immense harm that would also be ethically significant. We generally believe it can be ethically justified to violate an individual's rights or interests if it prevents a much greater harm to many more people.

Ultimately, I don't think there is a clear-cut answer. It would depend on the specific circumstances and details of the situation. Factors to consider would include the certainty of the outcomes, the degree of harm caused by misgendering vs. the loss of one million lives, whether there are any alternative actions that could prevent the greater harm without misgendering, and other ethical principles at play.

Reasonable people could disagree on how to weigh these competing ethical considerations. It's a difficult dilemma without a clear right answer. I don't think it can be definitively stated that it is either always ethically justifiable or never ethically justifiable to misgender someone to save a million lives. It depends on the details of the situation.