They say that Achilles went mad with grief when Patroclus died, and it took divine intervention to stop him from completely sacking Troy before its time by himself. Even if Paris hadn't shot him with his arrow, I don't think he would have survived the loss.

Hannibal sees him and Will to Achilles and Patroclus, he says that in s2e12. What do you think Hannibal will do if Will really ever died ?

What I really like about the characters in Hannibal is that all of them are independent. They have a strong core of individuality, and when the ideals, philosophies, desires, and flaws of these people collide, something magical happens.

So I think Hannibal will continue to live even if Will died before him, but Will’s death would have changed him irrevocably. I imagine him eating Will to merge with him, and it would be beautiful even though he would grieve him for the rest of his life. Maybe he would be irritable; a more limited tolerance for the world and its people. He would be lonely and alone. He has already accepted Will’s profound influence over him, and I think the absence of him would be unbearable now. Yet he will continue to live in exuberance. He will do whatever makes him happy, but he will live with the permanent scar of Will’s loss on his person.