Are we sure Scion have one, he is just a random dude from his race so he isn't a ultimate one, but he does come from a race of sufficiently godlike being so he might lack death as concept.
The Entities in the Wormverse and the Ultimate Ones from the Nasuverse are similar in few ways and different in MANY ways.
They are similar in that they are multi-dimensional and that they are aliens.
They are different in that they follow different Rules of Reality.
The Wormverse is supposed to be a very "Hard Science" reality.
Meaning, the same Laws of Physics as our world, no Gods or Souls or "Eezo"/Plot Mcguffins.
Apparently magic exists in Worm, according to WoG(for whatever that's worth), just nowhere near the Plot.
Also, Entropy affects EVERYTHING. Meaning EVERYTHING eventually dies.
The Nasuverse is in no way a "Hard Science" reality.
In the Nasuverse, Death is a Human Created phenomena.
As in, because enough people believed that you should Die when you are Killed, Conceptual Death came into being for All Earthlings, Retroactively. Thus if you were born, created, built or came into existence on Earth, you were then preloaded with the Concept of Death.
Mortal, Immortal, God, it doesn't matter.
If you are an "Earthling", SOMETHING can kill you.
This does not apply to the Ultimate Ones.
They do not have a Concept of Death.
Because they are not from Earth, thus were not affected by the "Common Sense of Man".
Atlas have something called Black Barrel.
It is metaphorically a hypodermic needle filled with Concept of Death, that can be "injected" into an Ultimate One.
Thus "infecting" them with the "Common Sense of Man", that states Everything Dies eventually.
Only then could you kill an Ultimate One.
Of course, good luck ever accomplishing either of those against an Ultimate One.
The Entities would have the Concept of Death simply due to the fact that they are seeking a solution to Entropy. Mainly so they can have infinite energy to fuel infinite breeding. But they also are seeking a way to avoid "The End" of the Universe. When all the stars die. When the quantum foam flatlines. When all energy in the universe runs out.
They also have anti-Entity weapons.
Otherwise, they wouldn't need to "Protect" so-called "Vital Shards".
The Entities are not one big Shard. They are ALL of the Shards at once, just "Aimed" or directed by the "Vital" Shards.
The problem however, is that to kill an Entities "Vital" shards would be the equivalent to killing the President and all of Congress. It can be done, but they would just be replaced by a new President and new Congressmen. The Country would still be there. Full of people to fill the gap.
It would cause all the other Shards to start competing to place themselves as the next collection of "Vital Shards" and the "Dead" Entity is suddenly "Revived" once a small collection of the "Strongest" and/or "Smartest" Shards are labeled as the new "Vital" Shards.
To Truly kill an Entity, you have to kill ALL of the Shards.
Every. Last. One.
Of the Trillions of them...
Because every one of them is basically a Baby Entity.
MEoDP could do it.
If Taylor could percieve something like that.
Since her Eyes are synched up with her Shard, her brain wouldn't be fried trying to "See" that Death Spot.
More likely?
Taylor would just "Kill" Scion's "Vital Shards" if she stabs him in his Death Spot.
Because those are the Shards that make up Scion.