If Levi Were To Die (Reactions In A Nutshell)
Eren: Would be an emotional wreck for weeks (Treat it as if Armin or Mikasa had died instead, but not AS bad... Sort of...). Afterwards, would see it as a melancholic event and a tragic, but meaningful death of a friend.
Mikasa: Would feel SUPER bad for Eren, but also would feel bad for treating Levi the way she did.
Armin: Would be upset that his friends feel bad, but would be mutual with feelings.
Jean: Would feel as if he had something to do with his death, even if he wasn't there.
Connie/Sasha: Would deal with it better than other people since they didn't really KNOW Levi, but would still treat it like a major loss.
Krysta: Will try to cheer everyone up again, but would pain her VERY much.
Erwin: DEPRESSED. FOR DAYS. Poor guy won't get his work done properly and would probably mourn for his friend every other day.
Hange: AGAIN, DEPRESSED. Even the Titans won't make her smile... And that means a lot. Would support Erwin, as same to her.