You got taste in anime.This too, but I first thought of Code Geass. It's exactly like the Lelouch vs Suzaku conflict
I also thought Dante went a little bit too far. Just chill out, dude
The red nephilim refusing to kill his brother for Kat was a sign of weakness. He claimed that he would of stop him from ruling the world, but when he was about to kill him, his words became meaningless.