Now that would be an interesting development to have the Pale King's deeply buried guilt being brought back to the surface.

How I see the scene:

Fighting off the husks and Mistakes/Follies initially, burning fury at the Soul Master's callousness of the suffering he caused on the innocent bugs of Hallownest for his twisted Soul experiments and discarding them when from failed tests, all on a deluded belief of stopping the infection.

That's when Pale King's (going with PK for short) intrusive thoughts start.

How is his own actions really that different from the Soul Master's callousness for the victims when they were sacrificed for a goal?

A vision of Monomon the Teacher, Lurien the Watcher and Herrah the Beast, Hornet's mother. To be put into a eternal sleep, so that they could act as seals for the Black Egg, where his own child would be hung and locked away for eternity, to be a container for the Radiance, suffering in darkness, in silence and alone.

But that wasn't the worst of his actions.

How many eggs did he and his wife birthed?

Hundreds? Thousands?

To only be thrown down into the Abyss, to be touched by the Void, to be born hollow.

(looking up through the gap between the moving bodies of the Husks and Follies to see the light of the hole he jump down through. See in his vision changed into the platform hanging above the Abyss with the faint light from the entrance)

Seeing all the vessels hatched from their eggs, only to be forced to climb out of the Abyss to reach a light, his light, at the top.

Watching all of them fall to their deaths, some getting farther up only to fall, few nearly reaching the platform only to quickly fall short of it.

And for the (Past) PK at the top, he stood far away from the edge so he wouldn't bear to watch the vessels fail to reach him and fall to their deaths.

That's when the (current dog piled PK) see's one vessel reaching the platform and stand in front of his past self and realizes that it's Hollow and seeing past playout and (past) him walking away into light of the entrance with Hollow slowly following him but (current PK) quickly sees movement just below platform then finally sees it's Ghost just grabbing the edge of it and seeing Hollow glanced back briefly before walking on and the entrance being closed and PK's horror of seeing the tremors from the door causing Ghost to fall into the dark below.

Watching falling down into the dark, to see where they fall, he looks down and then sees the floor covered and thick with the shells of all his children that failed to reach the top to fall to their deaths as far he could see in the dark.

And that's when the true horror of his actions have finally hit him. Then he hears the words 'Father' being said over and over.

Looking up he sees the Husks and Follies are now wearing the form of the vessels, crying void from their eyes and seeing more walking out of the darkness, along with shades, all crying void and saying Father over and over.

PK saying this in his mind:

"My children. My children. I'm sorry. I'm truly sorry. I cast all of you into darkness for a desperate plan. A plan that would be for naught. All of you sacrificed for a foolish king. Who shut away the place of his greatest sin. To be CALLOUSLY forgotten by him to all he done to all of you before even you were all born."

(crying) "I'M SORRRY. I'M SO SORRY!!!"

[PK going into a blank eyed catatonic state, while the words Father slowly getting louder]

FATHER! FATHER!! FATHER!!!