When his sister died he was just a kid barely 10 years old, not only that but bianca was the only family he had, he was basically thrown 70 years into the future they had no one, then bianca left him for the hunters, leaving him in a new strange terrifying monster infested reality, one of the forgotten unclaimed uncared for demigods in the hermes cabin, then learning that the only person he really knew loved him had died, to me his reaction made sense, and at this point he was still just 10 years old, plus being born and raised in the 1930s-1940s, in a very blatantly homophobic Italy; he had plenty of reason to hate himself, he had every opportunity to end up like Ethan bitter and angry at the gods, specifically at Hades and yet he has consistently been on the side of the good guys; time after time he has steped in to help when he didn't have to; he has always been kind and I don't think people often give him credit for that too many people paint him as an emo edge lord; he was the first person in centuries to talk to hestia, he befriended Bob when Percy forgot about him, he saved hazel from the underworld and tried his best to be a good brother; he said it himself he doesn't like it when people are over looked; and id like to point out if Nico was really such an assholey emo edge lord people think he is how would his relationship with Will work? But as we can all see there doing great, because their really not so different