Nero has not yet seen his father in his “better years”...
NERO DEFENCE TIME:
One of the things that saddens me in this fandom is the taking of things that happened in the games in a too literal way.
Nero gets called deadweight once, and that is his nickname until today. Many DMC fans believe he doesn't contribute to the team because of that one line.
It's important to remember Dante messes up. He also has lapses of judgement. Despite not knowing the full story, V believed the boy would defeat Urizen.
At the end of the game, Nero stops the fight between Dante and Vergil by making them see common ground and his habilities as a demon hunter. If he hadnt, the brothers would have killed eachother.
When Dante asks Nero to stay put while he goes to hell, Nero retorts with: "For you to call me deadweight again?" and Dante tries to explain himself. It shows how he didn't meant that to sting as much as it did.
Vergil trusts him so much he gives him the William Blake book, A LITERAL REPRESENTATION OF HIS HEART.
NERO IS PERFECT EXACTLY THE WAY HE IS, IN THIS ESSAY I WILL-