After playing 5 and then revisiting 4 I realized this song is meant for Vergil more than anyone. At first I thought it was for Nero. But Nero realizes what truly motivates him and in the subsequent scenes Vergil does the same. He realizes that it isn’t about just obtaining power but to use power to protect what he cares about. Which is his legacy, his father’s legacy. Nero didn’t want to lose what he had found and Vergil, despite his words didn’t want to either. This is why Vergil is my favorite video game character ever. And it’s done so well that it doesn’t take away from Nero’s development. It actually adds so much depth. He is a parallel of his father. “I always hated myself for not having enough strength.”
“This time I’m not letting you die”
He lost his devil bringer, a part of him. But once he finds out Vergil is his father and Dante his uncle, he wants to do everything to protect it, despite his anger, which unleashes his true power. Nero doesn’t want his legacy to be letting those he loves die. Vergil is the exact same. To the uninitiated Vergil is all about power but what’s behind that lust for power is his motivation to gain so much power that he’ll never lose anyone again.
“Might controls everything. Without strength you cannot protect anything. Let alone yourself.”
It’s all about motivation.
Even the lyrics speak of overcoming obstacles, redemption, rising again, strength and legacy.
Best game ever.

Poor Nero, he never forgot what Credo did for him and was not going to let anyone else die for his mistakes.

Dante finally accepted his demon side and Vergil his human side. And Nero gained enough power to protect his family. He did not let his uncle and father die like Credo which still haunts him.

Dante found a successor, someone who has the willfulness and strength of his father to protect humanity.
Vergil found that he has a son, something that can give meaning to all that power that he always has.
and Nero found his family, so he can make amends for his mistakes and will never be truly alone anymore.
"This is his legacy"

Remember: Just because we only saw Credo in Devil May 4 as a boss, we can't forget that he was technically the older step brother since his family adopted Nero. Meaning that the fight between both Sons of Sparda at the end of Devil May Cry 5 reminded Nero of the conflict he had with Credo, who he was unable to save AND that their last interaction with each other was a fight.

But this time, Nero was able to do something about siblings fighting.

"I couldn't protect Credo. To this day, I hate myself for not having enough strength... But this time is different. I swear! I'M NOT LETTING YOU DIE!"

When those voices deep within
Bring you down to your knees again,
Redemption calls onto
All of those who persist
With the strength of the few.

Don't come to question
All that you've known.
Remember, you are not alone.
I will be here,
Standing beside you.

There is no mountain
Too tall to overcome.
We will be as one.
You will rise again...
This is your legacy!

Don't come to question
All that you've known.
Remember, you are not alone.
I will be here,
Standing beside you.

There is no mountain
Too tall to overcome.
We will be as one.
You will rise again...
This is your legacy!
Rise again...
This is your legacy!

Did anyone else notice this subtly play when Dante was approaching his childhood home?

If you think about it, Nero is almost a parallel or even a reincarnation of Sparda due to their many similarities. Devil powers, fighting for love (Kyrie), prevented Dante and Vergil from killing each other. It's quite ironic and fitting because both sons inherited different personalities from their father and when one of them had a son of his own, he inherited traits from both uncle and dad which completes Sparda.

“It’s not about loss.
Strength is a choice.
Fighting like hell to protect what’s important!”

-Dante, Son of Eva

"There is no mountain too tall to overcome"... See, Vergil, you can still make things right. The mountain you raised between you, your brother and others isn't so tall it can not be overcomed.

“I couldn’t protect Credo. To this day, I hate myself for not having enough strength. But this time is different! I SWEAR!”

“I’M NOT LETTING YOU DIE!”

Hearing this kinda makes me wish Nero could meet his grandparents. Just to see that their union brought fourth a noble legacy.

It's sad to think that Dante only called Nero deadweight to try and deter him from joining the fight because he can't risk losing another family member, but Nero is also so hung up on that word because how much it stings to remind him that he couldn't protect/save Credo and he's determined to prove he's not a deadweight by also not letting another family member die.

This song is so haunting, beautiful, and tragic. I've seen people who say this is just Nero's song. Or it's Vergil's song. But I think this is all three of their songs. Dante, Vergil, and Nero. Nero and Vergil are pretty straight forward. This is Nero defining his legacy. Overcoming his limits and breaking through to his father and making up for his mistakes and failures. Vergil is overcoming his hatred and opening up his heart after feeling like it was his fault their mother was murdered by demons. But here's where you have to look a bit deeper. Dante is getting old. His character model shows as much. He's not going to be around forever but someone has to be strong enough to protect the humans when he's gone. One his last lines of the game show's his growth and him accepting that Nero is his legacy the person who will carry on protecting the world. "It's because you're here we can do this" Vergil could have closed that gateway to hell on his own. He's just as strong as Dante. But Dante has accepted that Nero is his legacy and the one who be his successor much like Dante was for Sparta. Then there's the whole Eva singing to her children theory that kinda doubles down on this idea. She's telling them that their fight is over and they can rest now that Nero is ready to protect the human world. Just a little thought that I had might be wrong but the fact that a 3 minute long song has so many layers and meanings is just awesome.

Theme of an entire Sparda family

This is totally Eva singing to her sons and grandson

Vergil: Don't you dare say it-!

Dante: JACKPOT!

The end of a beautiful, painful, sad, love, family and amazing STORY

Finally we got the sequel we deserved, for me this is my best DMC forever. Brothers reunite again son and father reunite and a new era will start with a new generation ( maybe ) DMC 6 I'll be waiting.

This might be lost in the comments, but I think of Vergil as an Anti-Hero. After all, he’s trying to get power to protect everything he loves and holds dear, even if it means throwing away his humanity. He feels so much regret from Eva’s death, that he thinks that if he’s just like his father Sparda with his power, he’ll be able to protect everything he holds dear just like his father.