Levi had accepted it.

Someone needs to slow the titans down, or else the mission won't work. Hange had volunteered, so Hange had been okay with giving their life to ensure the mission would go on. He's seen it happen many times; Erwin choosing to charge the beast titan and lead so many scouts to their death is what first comes to mind. Both are choosing to sacrifice their lives for humanity, as the many before them have done the same.

He accepts it, and he moves on. He knows it's what is best for the team; the only way to complete the mission.

And he knows that you know it too. You're not fighting him at all; you've accepted it, but you're not taking it well.

And that's what hurts most of all.