Neal’s death was karma because he got what he deserved.
It costs something to victimize yourself, be hateful and resentful to someone for so long. Even if it seems earned, rightful for someone to be so bitter at someone that has hurt them. You don’t hold onto that negativity for 300 years. Neal’s angst and all his issues, baggage and past pain was what he earned for hating Rumple for so long. That’s what dark magic is about, feeding off that negative energy. Neal may not have practice as much dark magic as Rumple but he’s guilty of practicing that mantra. Not being able to let go was Neal’s sin that needed to be paid for.
In alot of ways Neal’s dead was beautiful. Everything he had hated and judged Rumple for Neal did. Turning to dark magic, making rash decisions, lettings the ends justify the means and choosing to let go of his son. People can be angry at Neal for doing what Neal hated from his own father. But I think its poetic. Because Neal understands first hand all the pain and everything his father had gone through when he made these decisions. This is how we know Neal fully forgives his father now because when he was faced with the same tough decisions he made the same decisions as his father. He can’t hate him or say he doesn’t understand anymore. He finally understands all the pain and love Rumple had. That’s healing, that resulted in Neal’s death but it was a journey worth taking because it melted away all the baggage and past issues of the monster he made his father out to be.
If he was going to die at least everything he father had ever ever done was redeemed and it was also redeemed for Henry. To learn what being selfless truly is for someone you truly love. Even though being with them is all you ever wanted and did anything for. Learning to let go of those dreams and desires so that your children can have their best chance is the ultimate sacrifice. Its what Rumple and Neal both learned so that Henry can hopefully not have to learn it the hard way.