I can see the sense behind "the Pale Kings plan was doomed from the start because creating a perfect pure vessel was never feasible" but I have a hard time letting go of the tragedy of the idea that it was because he, in the end, couldnt fully abandon his humanity and remain personally cruel/cold enough to the Hollow Knight to see it through.
Frankly, that's what damns him to me. He had a flawed premise, he slaughtered hundreds of thousands of children on that flawed premise, and then when he found out that it wasn't going to work, and as the entirety of the game shows, it would never have worked (though who knows if he realized this), he doubled down on it and went through with it anyway. Love was not enough to stay his hand. No amount of love, perhaps, would have ever been enough. I have talked a little about this before, but in sealing the Abyss and leaving these words behind:
Our pure Vessel has ascended.
Beyond lies only the refuse and regret of its creation.
We shall enter that place no longer.
In a game where 'being forgotten is the only death that matters'? In a game where the Pale King temporarily defeated his greatest enemy and rival god by having everyone forget her and never again acknowledge her existence?
He gave his hundreds upon hundreds of dead children the same fate as he gave to Radiance, his rival and enemy; to be condemned, forgotten. The ultimate death, never to be acknowledged or mourned.
(and just like radiance they all came crawling back out again lol)
And it was for the love of his kingdom that others were subjugated and made subordinate to it, after all! Love is a neutral emotion, its results can be good or bad. In PK's case it generally did turn out badly.
Tragedy certainly exists in the narrative, but not a lot of it belongs to the Pale King, I feel. If anything he's more pitiful than truly tragic to me.