If you could kill off one of the scions...

[Tenkuu]

All this hate to dragons, the dragoons, etc. All this is a culture imprigned on Ishgardians beacuse they learn that dragons are their enemie, why their enemie beacuse they have atacked and killed countless of people. All this beacuse of the war they have between them, so yea they learn to fear and hate dragons. But is not their fault

I think you are confusing trust with an eternal revengue with people who are innocent about something that happened 100 years ago. With the trust, yea I understand Hraesvelgr 's point. But Nidhogg is a different story, you cannot say that his actions arent guilty and it was on his "hands" to stop the war.

Both dragons know very well the life's spawn of humans, they just dont care

I'm not really sure what part of what I've said you're quoting, but here goes. Exactly, Isgardians are taught ignorance and lies. Even so, it should be obvious to them that by continuing to kill dragons, they're not exactly fomenting positive relationships with them. So then, how is that supposed to redeem them in the eyes of any Dravanian? The Ishgardians have never looked for a solution the way the Scions did, instead they simply painted themselves as victims and resigned themselves to eternally go "woe is me".

What reason did Nidhogg have to want to stop a war that, in his eyes, he did not begin nor was responsible for? To him, the Ishgardians are responsible for everything, both the initial killing of his sister and the perpetuation of a tradition of killing dragons.

Nidhogg does not feel that any Ishgardians deserve to live because he believes them all untrustworthy and more than capable of repeating a betrayal if they were to be trusted again.

Tenku, my apologies for this question, Did you watch the cutscenes of 3.0?

Estinien, Hraesvelgr and Middy made clear that Nidhogg was beyong reasoning and that his vengeance was insatiable. Yes, Nidhogg was the first one to find out that his sister was dead, Hraesvelgr told us that

I dont think Midgarsormr was meaning that he will join the dragonsong war. He pretty much is on a neutral state.

Keeper of the Lake is 2.0 content, not 3.0, and Midgarsormr made clear at the time that he was reviving to join the chorus begun by his child. Yes, I've seen all of the cutscenes, the story is much more important to me than the quests themselves. I'm not saying that Nidhogg is entirely in the right btw, I'm just arguing that I can definitely see it from his point of view.